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Plant Signaling & Behavior Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/kpsb20
Stress response of OsETHE1 is altered in response to light and dark conditions a
a
ab
Charanpreet Kaur , Sneh Lata Singla-Pareek & Sudhir K Sopory a
Plant Molecular Biology Group, International Center for Genetic Engineering and Biotechnology; Aruna Asaf Ali Marg; New Delhi, India b
Jawaharlal Nehru University; Aruna Asaf Ali Marg; New Delhi, India Accepted author version posted online: 31 Oct 2014.Published online: 24 Dec 2014.
Click for updates To cite this article: Charanpreet Kaur, Sneh Lata Singla-Pareek & Sudhir K Sopory (2014) Stress response of OsETHE1 is altered in response to light and dark conditions, Plant Signaling & Behavior, 9:11, e973820, DOI: 10.4161/15592324.2014.973820 To link to this article: http://dx.doi.org/10.4161/15592324.2014.973820
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
SHORT COMMUNICATION Plant Signaling & Behavior 9:11, e973820; December 1, 2014; © 2014 Taylor & Francis Group, LLC
Stress response of OsETHE1 is altered in response to light and dark conditions Charanpreet Kaur1,*, Sneh Lata Singla-Pareek1, and Sudhir K Sopory1,2 1
Plant Molecular Biology Group, International Center for Genetic Engineering and Biotechnology; Aruna Asaf Ali Marg; New Delhi, India; 2Jawaharlal Nehru University; Aruna Asaf Ali Marg; New Delhi, India
Downloaded by [Michigan State University] at 21:32 12 January 2015
Keywords: ETHE1, light, rice, sulfur metabolism, stress
ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 (ETHE1), encoding sulfur dioxygenase activity is believed to be an important candidate in sulfur metabolism, where it is involved in amino acid catabolism during carbohydrate starvation and embryo development as seen in Arabidopsis thaliana. OsETHE1, an ETHE1-encoding gene from rice, is in fact induced in response to abiotic stresses, condition which affects nutritional status of the plant, reflecting the need for nutrient remobilization. Sulfur reduction and assimilation are believed to be light-dependent processes and so the genes involved in sulfur oxidation must also be investigated for light-dependent regulatory effects. To this end, we show that the stress response of OsETHE1 is dependent on light and that darkness largely suppresses the stress response of this gene. However, the observed regulatory effect is intricate, varying according to the stress imposed; thereby suggesting the involvement of various aspects of signaling in this process.
ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 (ETHE1) encodes a mitochondrial sulfur dioxygenase (SDO) activity, involved in the oxidation of sulfides or persulfides derived from amino acids to thiosulfate and sulfate.1,2 Being present in a wide range of organisms, including bacteria, plants and humans; ETHE1 is believed to be an important candidate involved in sulfur metabolism. In humans, mutations in ETHE1 lead to a fatal metabolic disease ethylmalonic encephalopathy3, which is characterized by an increase in sulfide concentration in the bloodstream, severely damaging vascular endothelium and thus causing main symptoms of the disease.4 In Arabidopsis thaliana, ETHE1 has been shown to be critical for seed development1 and other conditions that involve high protein turnover, and is also involved in the use of amino acids as alternative respiratory substrates.2 Being part of the mitochondrial sulfur catabolic pathway, AtETHE1 is upregulated in conditions that stimulate nutrient remobilization, such as prolonged darkness, drought, abscisic acid, germination or unfavorable conditions leading to carbohydrate starvation.2 Nutrient remobilization is known to generally occur in stress, as a part of metabolic adaptations in order to prevent starvation and to balance the energy status of the system.5 Sulfur metabolism is specifically important as it forms the basis of important sulfur containing-defense compounds, i.e. elemental sulfur, hydrogen peroxide, glutathione and phytochelatins. Thus, ETHE1 proteins involved in sulfide detoxification are believed to be important in stress response as well. In rice, we have recently reported the presence of an ETHE1like protein, OsETHE1, which is involved in abiotic stress response.6 Like AtETHE1, OsETHE1 is believed to be involved
in mitochondrial sulfur metabolism considering high similarity in amino acid sequences and thus, biochemical activity of the 2 mitochondrial proteins. OsETHE1 was found to be highly expressed in roots and analysis of OsETHE1-promoter:GUS plants revealed its increased expression in various stress conditions, including high temperature, oxidative stress, ABA and methylglyoxal (MG) treatments.6 Roots are metabolically active and growing tissues which undergo high protein turnover and also sulfate acquired by roots constitutes the primary sulfur source for growth, thereby justifying the role of OsETHE1 as a part of sulfur catabolism pathway in roots. However, OsETHE1 is also expressed in shoots though at significantly lower levels. This observation is in contrast to available reports that describe sulfur reduction in plants as a light-enhanced process that predominantly takes place in leaves rather than roots.7 Nevertheless, expression analysis of OsETHE1 in shoots revealed alteration in OsETHE1 transcript profile in response to stress, indicating its role in stress-induced metabolic functioning in shoots as well (Fig. 1). Further, OsETHE1 expression was induced in response to multiple stresses such as, salinity, oxidative, high and low temperature treatments in shoots of salt-tolerant Pokkali rice which also indicated toward important role of rice ETHE1 in shoots (Fig. 1). In fact, in Pokkali rice, OsETHE1 transcript levels were found to be induced earlier (at 6 h) under all the stress conditions tested except wounding, when compared to salt-sensitive IR64 rice (Fig. 1A). In addition, expression of OsETHE1 in Pokkali was also induced by drought stress but only after 24 h of the treatment (Fig. 1B). However, in the salt-sensitive rice IR64, OsETHE1 is induced only under high temperature and
*Correspondence to: Charanpreet Kaur; Email: [email protected] Submitted: 07/11/2014; Revised: 08/05/2014; Accepted: 08/06/2014 http://dx.doi.org/10.4161/15592324.2014.973820
www.landesbioscience.com
Plant Signaling & Behavior
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Downloaded by [Michigan State University] at 21:32 12 January 2015
expression of OsETHE1 is also induced early on exposure to multiple abiotic stress conditions in salt-tolerant Pokkali rice (Fig. 1A). Interestingly, expression of OsETHE1 is affected by light/dark conditions. In order to investigate whether stress response of OsETHE1 is regulated by light, we checked the effect of salinity, ABA and MG treatments on OsETHE1 promoter activity in presence and absence of light at 6 h and 24 h of stress (Fig. 2); conditions which we have previously observed to induce Figure 1. Expression analysis of OsETHE1 in salt sensitive and tolerant rice genotypes, IR64 and Pokkali, in response to different abiotic stress treatments at 6 h (A) and 24 h (B). Real time PCR analysis was OsETHE1 expression.6 Importantly, done using cDNA template generated from shoot tissue of 14 d old stressed or control seedlings. For dark-germinated transgenic promoter cold or heat treatment, seedlings kept in Yoshida medium were transferred to a cold chamber mainlines when subjected to either ABA or tained at 4 § 1 C or an incubator at 42 § 1 C, respectively. For drought, seedlings were removed MG treatments exhibited a reduced from medium and air dried on a 3-mm blotting paper. For mechanical wounding, each leaf of seedresponse as compared to light-grown lings was given a small cut with a blade. For salinity, MG and oxidative stress, seedlings were kept in Yoshida medium supplied with 200 mM NaCl, 5 mM MG, or 5 mM hydrogen peroxide, respectively. seedlings, in both roots and shoots Fold change in expression has been indicated in log2 scale. The bars above or below 0 shows the tran(Fig. 2A and B). Upon ABA treatment script upregulation and downregulation, respectively. under normal light conditions, promoter activity increased at 6 h but wounding stress within 6 h of the treatment (Fig. 1A) and in dropped at 24 h; in contrast in dark conditions, promoter activsalinity within 24 h of the treatment (Fig. 1B). It is a common ity decreased at 6 h but increased at 24 h, following a reverse patobservation that genes involved in stress adaptation responses in tern. MG treatment led to a different pattern of regulation where plants are maintained at and induced to higher levels in stress-tol- promoter activity increased at both 6 h and 24 h in roots and erant varieties when compared to stress-sensitive ones, indicating shoots of light-grown seedlings (Fig. 2B). Dark conditions led to their preparedness toward adverse situations.8,9 Likewise, decline in promoter activity at both time points but did not alter
Figure 2. Measurement of GUS activity in root and shoot tissues of OsETHE1 promoter-GUS transgenic seedlings grown in complete dark or control light conditions in response to ABA (A), MG (B) and salt (C) treatment at 6 h and 24 h. 100 mM ABA, 5 mM MG or 200 mM NaCl (for salinity stress) were used for the respective treatments. Activity is expressed as percentage relative to that observed at 0 h in root (taken as 100%). Data is presented as the mean (§ standard error) of GUS activity determined from 2 independent transgenic lines and experiment was repeated thrice.
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the pattern of regulation. In response to salinity treatment, an altogether different pattern of regulation could be observed as compared to ABA and MG treatments (Fig. 2C). Dark germinated seedlings exhibited increased activity of the promoter at 6 h in both shoots and roots as compared to light-grown seedlings after NaCl treatment. But at 24 h, promoter activity was lower as compared to that observed in light-grown seedlings. The regulatory effect of light on OsETHE1 expression under stress seems to be complex as otherwise OsETHE1 promoter activity was only marginally reduced under non-stress conditions in dark-germinated seedlings. In contrast, in Arabidopsis extended darkness has been reported to induce AtETHE1 expression where it is involved in protein turnover processes.2 Collectively, light has a pronounced effect on stress response of OsETHE1 in both roots and shoots, much like the sulfur assimilation pathway leading to H2S emission which is highly dependent on photosynthetic electron transport, with reduced H2S emission in dark except when L-cysteine is supplied.10 However, in roots, dependence of stress response on light still remains unexplained which can possibly occur through transmission of light signals from shoots to roots. Another possibility is the References 1. Holdorf MM, Owen HA, Lieber SR, Yuan L, Adams N, Dabney-Smith C, Makaroff CA. Arabidopsis ETHE1 encodes a sulfur dioxygenase that is essential for embryo and endosperm development. Plant Physiol 2012; 160:226-236; PMID:22786886; http://dx.doi. org/10.1104/pp.112.201855 2. Kr€ ußel L, Junemann J, Wirtz M, Birke H, Thornton JD, Browning LW, Poschet G, Hell R, Balk J, Braun HP et al. The mitochondrial sulfur dioxygenase ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 is required for amino acid catabolism during carbohydrate starvation and embryo development in Arabidopsis. Plant Physiol 2014; 165:92-104; http://dx.doi.org/ 10.1104/pp.114.239764 3. Tiranti V, D’Adamo P, Briem E, Ferrari G, Mineri R, Lamantea E, Mandel H, Balestri P, Garcia-Silva MT, Vollmer B, et al. Ethylmalonic encephalopathy is caused by mutations in ETHE1, a gene encoding a mitochondrial matrix protein. Am J Hum Genet 2004; 74:239-252; PMID:14732903; http://dx.doi.org/ 10.1086/381653
www.landesbioscience.com
existence of some interaction between shoots and roots related to sulfur metabolism, where sulfur availability in leaves, which is light-dependent, is conveyed to roots, thereby resulting in indirect regulation of OsETHE1 by light in roots. Supporting this, an interaction between metabolism of atmospheric H2S in the shoot and sulfate uptake in roots has been reported in Brassica oleracea.11 To conclude, we believe OsETHE1 expression is important in stress in both shoots and roots and light plays an important but multifaceted role in regulation of this response.
Disclosure of Potential Conflicts of Interest
No potential conflicts of interest were disclosed.
Funding
This work was supported by internal grants of International Center for Genetic Engineering and Biotechnology (ICGEB), India and Department of Biotechnology (DBT), Government of India.
4. Giordano C, Viscomi C, Orlandi M, Papoff P, Spalice A, Burlina A, Meo I, Tiranti V, Leuzzi V, d’Amati G, et al. Morphologic evidence of diffuse vascular damage in human and in the experimental model of ethylmalonic encephalopathy. J Inherit Metab Dis 2012; 35:451-458; PMID:22020834; http://dx.doi.org/ 10.1007/s10545-011-9408-3 5. Alam SM. Handbook of plant and crop stress. 2nd ed. USA: Marcel Dekker; 1999. Chapter 12, Nutrient uptake by plants under stress conditions; 285-313. 6. Kaur C, Mustafiz A, Sarkar AK, Ariyadasa TU, SinglaPareek SL, Sopory SK. Expression of abiotic stress inducible ETHE1-like protein from rice is higher in roots and is regulated by calcium. Physiol Plant 2014; 152:1-16; PMID:24410953; http://dx.doi.org/ 10.1111/ppl.12147 7. Rennenberg H, Schmitz K, Bergmann L. Long-distance transport of sulfur in Nicotiana tabacum. Planta 1979; 147:57-62; PMID:24310895; http://dx.doi.org/ 10.1007/BF00384591 8. Kumar G, Purty RS, Singla-Pareek SL, Pareek A. Maintenance of stress related transcripts in tolerant
Plant Signaling & Behavior
cultivar at a level higher than sensitive one appears to be a conserved salinity response among plants. Plant Signal Behav 2009; 4:431-434; PMID:19816099; http://dx.doi.org/10.4161/psb.4.5.8298 9. El-Shabrawi H, Kumar B, Kaul T, Reddy MK, SinglaPareek SL, Sopory SK. Redox homeostasis, antioxidant defense, and methylglyoxal detoxification as markers for salt tolerance in Pokkali rice. Protoplasma 2010; 245:85-96; PMID:20419461; http://dx.doi.org/ 10.1007/s00709-010-0144-6 10. Rennenberg H, Sekija J, Wilson LG, Filner P. Evidence for an intracellular sulfur cycle in cucumber leaves. Planta 1982; 154:516-524; PMID:24276346; http:// dx.doi.org/10.1007/BF00402995 11. Westerman S, De Kok LJ, Elisabeth C, Stuiver E, Stulen I. Interaction between metabolism of atmospheric H2S in the shoot and sulfate uptake by the roots of curly kale (Brassica oleracea). Physiol Plant 2000; 109:443-449; http://dx.doi.org/10.1034/j.13993054.2000.100411.x
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Plant Signaling & Behavior Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/kpsb20
Stress response of OsETHE1 is altered in response to light and dark conditions a
a
ab
Charanpreet Kaur , Sneh Lata Singla-Pareek & Sudhir K Sopory a
Plant Molecular Biology Group, International Center for Genetic Engineering and Biotechnology; Aruna Asaf Ali Marg; New Delhi, India b
Jawaharlal Nehru University; Aruna Asaf Ali Marg; New Delhi, India Accepted author version posted online: 31 Oct 2014.Published online: 24 Dec 2014.
Click for updates To cite this article: Charanpreet Kaur, Sneh Lata Singla-Pareek & Sudhir K Sopory (2014) Stress response of OsETHE1 is altered in response to light and dark conditions, Plant Signaling & Behavior, 9:11, e973820, DOI: 10.4161/15592324.2014.973820 To link to this article: http://dx.doi.org/10.4161/15592324.2014.973820
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
SHORT COMMUNICATION Plant Signaling & Behavior 9:11, e973820; December 1, 2014; © 2014 Taylor & Francis Group, LLC
Stress response of OsETHE1 is altered in response to light and dark conditions Charanpreet Kaur1,*, Sneh Lata Singla-Pareek1, and Sudhir K Sopory1,2 1
Plant Molecular Biology Group, International Center for Genetic Engineering and Biotechnology; Aruna Asaf Ali Marg; New Delhi, India; 2Jawaharlal Nehru University; Aruna Asaf Ali Marg; New Delhi, India
Downloaded by [Michigan State University] at 21:32 12 January 2015
Keywords: ETHE1, light, rice, sulfur metabolism, stress
ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 (ETHE1), encoding sulfur dioxygenase activity is believed to be an important candidate in sulfur metabolism, where it is involved in amino acid catabolism during carbohydrate starvation and embryo development as seen in Arabidopsis thaliana. OsETHE1, an ETHE1-encoding gene from rice, is in fact induced in response to abiotic stresses, condition which affects nutritional status of the plant, reflecting the need for nutrient remobilization. Sulfur reduction and assimilation are believed to be light-dependent processes and so the genes involved in sulfur oxidation must also be investigated for light-dependent regulatory effects. To this end, we show that the stress response of OsETHE1 is dependent on light and that darkness largely suppresses the stress response of this gene. However, the observed regulatory effect is intricate, varying according to the stress imposed; thereby suggesting the involvement of various aspects of signaling in this process.
ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 (ETHE1) encodes a mitochondrial sulfur dioxygenase (SDO) activity, involved in the oxidation of sulfides or persulfides derived from amino acids to thiosulfate and sulfate.1,2 Being present in a wide range of organisms, including bacteria, plants and humans; ETHE1 is believed to be an important candidate involved in sulfur metabolism. In humans, mutations in ETHE1 lead to a fatal metabolic disease ethylmalonic encephalopathy3, which is characterized by an increase in sulfide concentration in the bloodstream, severely damaging vascular endothelium and thus causing main symptoms of the disease.4 In Arabidopsis thaliana, ETHE1 has been shown to be critical for seed development1 and other conditions that involve high protein turnover, and is also involved in the use of amino acids as alternative respiratory substrates.2 Being part of the mitochondrial sulfur catabolic pathway, AtETHE1 is upregulated in conditions that stimulate nutrient remobilization, such as prolonged darkness, drought, abscisic acid, germination or unfavorable conditions leading to carbohydrate starvation.2 Nutrient remobilization is known to generally occur in stress, as a part of metabolic adaptations in order to prevent starvation and to balance the energy status of the system.5 Sulfur metabolism is specifically important as it forms the basis of important sulfur containing-defense compounds, i.e. elemental sulfur, hydrogen peroxide, glutathione and phytochelatins. Thus, ETHE1 proteins involved in sulfide detoxification are believed to be important in stress response as well. In rice, we have recently reported the presence of an ETHE1like protein, OsETHE1, which is involved in abiotic stress response.6 Like AtETHE1, OsETHE1 is believed to be involved
in mitochondrial sulfur metabolism considering high similarity in amino acid sequences and thus, biochemical activity of the 2 mitochondrial proteins. OsETHE1 was found to be highly expressed in roots and analysis of OsETHE1-promoter:GUS plants revealed its increased expression in various stress conditions, including high temperature, oxidative stress, ABA and methylglyoxal (MG) treatments.6 Roots are metabolically active and growing tissues which undergo high protein turnover and also sulfate acquired by roots constitutes the primary sulfur source for growth, thereby justifying the role of OsETHE1 as a part of sulfur catabolism pathway in roots. However, OsETHE1 is also expressed in shoots though at significantly lower levels. This observation is in contrast to available reports that describe sulfur reduction in plants as a light-enhanced process that predominantly takes place in leaves rather than roots.7 Nevertheless, expression analysis of OsETHE1 in shoots revealed alteration in OsETHE1 transcript profile in response to stress, indicating its role in stress-induced metabolic functioning in shoots as well (Fig. 1). Further, OsETHE1 expression was induced in response to multiple stresses such as, salinity, oxidative, high and low temperature treatments in shoots of salt-tolerant Pokkali rice which also indicated toward important role of rice ETHE1 in shoots (Fig. 1). In fact, in Pokkali rice, OsETHE1 transcript levels were found to be induced earlier (at 6 h) under all the stress conditions tested except wounding, when compared to salt-sensitive IR64 rice (Fig. 1A). In addition, expression of OsETHE1 in Pokkali was also induced by drought stress but only after 24 h of the treatment (Fig. 1B). However, in the salt-sensitive rice IR64, OsETHE1 is induced only under high temperature and
*Correspondence to: Charanpreet Kaur; Email: [email protected] Submitted: 07/11/2014; Revised: 08/05/2014; Accepted: 08/06/2014 http://dx.doi.org/10.4161/15592324.2014.973820
www.landesbioscience.com
Plant Signaling & Behavior
e973820-1
Downloaded by [Michigan State University] at 21:32 12 January 2015
expression of OsETHE1 is also induced early on exposure to multiple abiotic stress conditions in salt-tolerant Pokkali rice (Fig. 1A). Interestingly, expression of OsETHE1 is affected by light/dark conditions. In order to investigate whether stress response of OsETHE1 is regulated by light, we checked the effect of salinity, ABA and MG treatments on OsETHE1 promoter activity in presence and absence of light at 6 h and 24 h of stress (Fig. 2); conditions which we have previously observed to induce Figure 1. Expression analysis of OsETHE1 in salt sensitive and tolerant rice genotypes, IR64 and Pokkali, in response to different abiotic stress treatments at 6 h (A) and 24 h (B). Real time PCR analysis was OsETHE1 expression.6 Importantly, done using cDNA template generated from shoot tissue of 14 d old stressed or control seedlings. For dark-germinated transgenic promoter cold or heat treatment, seedlings kept in Yoshida medium were transferred to a cold chamber mainlines when subjected to either ABA or tained at 4 § 1 C or an incubator at 42 § 1 C, respectively. For drought, seedlings were removed MG treatments exhibited a reduced from medium and air dried on a 3-mm blotting paper. For mechanical wounding, each leaf of seedresponse as compared to light-grown lings was given a small cut with a blade. For salinity, MG and oxidative stress, seedlings were kept in Yoshida medium supplied with 200 mM NaCl, 5 mM MG, or 5 mM hydrogen peroxide, respectively. seedlings, in both roots and shoots Fold change in expression has been indicated in log2 scale. The bars above or below 0 shows the tran(Fig. 2A and B). Upon ABA treatment script upregulation and downregulation, respectively. under normal light conditions, promoter activity increased at 6 h but wounding stress within 6 h of the treatment (Fig. 1A) and in dropped at 24 h; in contrast in dark conditions, promoter activsalinity within 24 h of the treatment (Fig. 1B). It is a common ity decreased at 6 h but increased at 24 h, following a reverse patobservation that genes involved in stress adaptation responses in tern. MG treatment led to a different pattern of regulation where plants are maintained at and induced to higher levels in stress-tol- promoter activity increased at both 6 h and 24 h in roots and erant varieties when compared to stress-sensitive ones, indicating shoots of light-grown seedlings (Fig. 2B). Dark conditions led to their preparedness toward adverse situations.8,9 Likewise, decline in promoter activity at both time points but did not alter
Figure 2. Measurement of GUS activity in root and shoot tissues of OsETHE1 promoter-GUS transgenic seedlings grown in complete dark or control light conditions in response to ABA (A), MG (B) and salt (C) treatment at 6 h and 24 h. 100 mM ABA, 5 mM MG or 200 mM NaCl (for salinity stress) were used for the respective treatments. Activity is expressed as percentage relative to that observed at 0 h in root (taken as 100%). Data is presented as the mean (§ standard error) of GUS activity determined from 2 independent transgenic lines and experiment was repeated thrice.
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Downloaded by [Michigan State University] at 21:32 12 January 2015
the pattern of regulation. In response to salinity treatment, an altogether different pattern of regulation could be observed as compared to ABA and MG treatments (Fig. 2C). Dark germinated seedlings exhibited increased activity of the promoter at 6 h in both shoots and roots as compared to light-grown seedlings after NaCl treatment. But at 24 h, promoter activity was lower as compared to that observed in light-grown seedlings. The regulatory effect of light on OsETHE1 expression under stress seems to be complex as otherwise OsETHE1 promoter activity was only marginally reduced under non-stress conditions in dark-germinated seedlings. In contrast, in Arabidopsis extended darkness has been reported to induce AtETHE1 expression where it is involved in protein turnover processes.2 Collectively, light has a pronounced effect on stress response of OsETHE1 in both roots and shoots, much like the sulfur assimilation pathway leading to H2S emission which is highly dependent on photosynthetic electron transport, with reduced H2S emission in dark except when L-cysteine is supplied.10 However, in roots, dependence of stress response on light still remains unexplained which can possibly occur through transmission of light signals from shoots to roots. Another possibility is the References 1. Holdorf MM, Owen HA, Lieber SR, Yuan L, Adams N, Dabney-Smith C, Makaroff CA. Arabidopsis ETHE1 encodes a sulfur dioxygenase that is essential for embryo and endosperm development. Plant Physiol 2012; 160:226-236; PMID:22786886; http://dx.doi. org/10.1104/pp.112.201855 2. Kr€ ußel L, Junemann J, Wirtz M, Birke H, Thornton JD, Browning LW, Poschet G, Hell R, Balk J, Braun HP et al. The mitochondrial sulfur dioxygenase ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 is required for amino acid catabolism during carbohydrate starvation and embryo development in Arabidopsis. Plant Physiol 2014; 165:92-104; http://dx.doi.org/ 10.1104/pp.114.239764 3. Tiranti V, D’Adamo P, Briem E, Ferrari G, Mineri R, Lamantea E, Mandel H, Balestri P, Garcia-Silva MT, Vollmer B, et al. Ethylmalonic encephalopathy is caused by mutations in ETHE1, a gene encoding a mitochondrial matrix protein. Am J Hum Genet 2004; 74:239-252; PMID:14732903; http://dx.doi.org/ 10.1086/381653
www.landesbioscience.com
existence of some interaction between shoots and roots related to sulfur metabolism, where sulfur availability in leaves, which is light-dependent, is conveyed to roots, thereby resulting in indirect regulation of OsETHE1 by light in roots. Supporting this, an interaction between metabolism of atmospheric H2S in the shoot and sulfate uptake in roots has been reported in Brassica oleracea.11 To conclude, we believe OsETHE1 expression is important in stress in both shoots and roots and light plays an important but multifaceted role in regulation of this response.
Disclosure of Potential Conflicts of Interest
No potential conflicts of interest were disclosed.
Funding
This work was supported by internal grants of International Center for Genetic Engineering and Biotechnology (ICGEB), India and Department of Biotechnology (DBT), Government of India.
4. Giordano C, Viscomi C, Orlandi M, Papoff P, Spalice A, Burlina A, Meo I, Tiranti V, Leuzzi V, d’Amati G, et al. Morphologic evidence of diffuse vascular damage in human and in the experimental model of ethylmalonic encephalopathy. J Inherit Metab Dis 2012; 35:451-458; PMID:22020834; http://dx.doi.org/ 10.1007/s10545-011-9408-3 5. Alam SM. Handbook of plant and crop stress. 2nd ed. USA: Marcel Dekker; 1999. Chapter 12, Nutrient uptake by plants under stress conditions; 285-313. 6. Kaur C, Mustafiz A, Sarkar AK, Ariyadasa TU, SinglaPareek SL, Sopory SK. Expression of abiotic stress inducible ETHE1-like protein from rice is higher in roots and is regulated by calcium. Physiol Plant 2014; 152:1-16; PMID:24410953; http://dx.doi.org/ 10.1111/ppl.12147 7. Rennenberg H, Schmitz K, Bergmann L. Long-distance transport of sulfur in Nicotiana tabacum. Planta 1979; 147:57-62; PMID:24310895; http://dx.doi.org/ 10.1007/BF00384591 8. Kumar G, Purty RS, Singla-Pareek SL, Pareek A. Maintenance of stress related transcripts in tolerant
Plant Signaling & Behavior
cultivar at a level higher than sensitive one appears to be a conserved salinity response among plants. Plant Signal Behav 2009; 4:431-434; PMID:19816099; http://dx.doi.org/10.4161/psb.4.5.8298 9. El-Shabrawi H, Kumar B, Kaul T, Reddy MK, SinglaPareek SL, Sopory SK. Redox homeostasis, antioxidant defense, and methylglyoxal detoxification as markers for salt tolerance in Pokkali rice. Protoplasma 2010; 245:85-96; PMID:20419461; http://dx.doi.org/ 10.1007/s00709-010-0144-6 10. Rennenberg H, Sekija J, Wilson LG, Filner P. Evidence for an intracellular sulfur cycle in cucumber leaves. Planta 1982; 154:516-524; PMID:24276346; http:// dx.doi.org/10.1007/BF00402995 11. Westerman S, De Kok LJ, Elisabeth C, Stuiver E, Stulen I. Interaction between metabolism of atmospheric H2S in the shoot and sulfate uptake by the roots of curly kale (Brassica oleracea). Physiol Plant 2000; 109:443-449; http://dx.doi.org/10.1034/j.13993054.2000.100411.x
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