BIOCHEMICAL

Vol. 84, No. 4, 1978

AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages

October 30,1978

: NOT A PREREQUISITE

CHEMOTAXIS

993-997

FOR PLASMODIA COALESCENCE

IN PHYSARUM POLYCEPHALUM Wung-Wai *Department

of Biochemistry,

Tso*

The Chinese

Hong Kong and Radioisotope Received

August

and Man-Yin

Unit,

Wong

University

of Hong Kong,

University

of Hong‘Kong,

Shatin,

N.T.,

Hong Kong

11,1978 SUMMARY

Unlike pseudoplasmodium formation in Dictyostelium discoideum which involves the aggregation of amaebae chemotactically responding to pulses of cyclic AMP released from pacemaker cells, the plasmodia and presumably the microplasmodia of Physarum polycephalum coalesce without the presence of a chemotactic stimulus. INTRODUCTION Myxomycetes, Acrasiales,

the acellular

the cellular

slime

exhibit

many similar

perform

tactically

oriented

including

those

from heat

with

are washed

a non-nutrient

plasmodium

which

plasmodium

is

amaebae cyclic

free

contains

(2,3),

generate

AMP at intervals

signalling

molecules

an inward

chemotactic

(4,5)

of nutrient

movement.

cells

Myxomycetes

they

motile

to various

external (6-8,

AMP releasing signals

3 to 10 minutes to reach is

proposed

that

an humidified a pseudo-

of the pseudo-

designed

by sending

the peripherous

1, 9-12).

to form

pacemaker

(14,15).

stimuli

on filters

The formation event

phases

discodeum,

aggregate

biochemical

to

and Acrasiales

vegetative

and chemicals

(13).

cyclic

It

to be related

of Dictyostelium

solution,

the aggregation

out

thought

medium and dispersed

programmed

between diffuse

Both Their

amaebae

salt

are

in response

light

Some autonomously

population

(1).

movement

103-lo5

a well

molds,

features.

grown

buffered

indeed

communication.

molds

behavioural

When logarithmically Acrasiale,

slime

for cells out

in the

a pulse

These

pulsatile

cells

which

the signal

social

of

trigger

reception

0006-291X/78/0844-0993$01.00/0 993

Copyright All rights

0 1978 by Academic Press, Inc. of reproduction in any form reserved.

Vol. 84, No. 4, 1978

mechanism cell

BIOCHEMICAL

involves

bound

a presumed

through presumably

from

and cover

gated

or spirals

period

programmed

inward

which

moves in a co-ordinated

large

plasmodium

grows, Like

polycephalum

involves

microplasmodia

when allowed a growing

to get plasmodium

over

into

sporulates

in g.

but

coalesce, into

contact

can reach

our observation

coalescence

of plasmodia

that

outward

in

source

go

the

AMP signal, about

As a result

100 seconds of this

movement,

by a slime

the aggre-

sheath

to form pseudophasmodium of Physarum

(17)

the existing

smaller

(20).

in -P. polyceaphalum event

a widely (18).

This

on the nature

the coalescence

separated

The size

a chemotactic

plasmodium

depending

discodeum,

in

polycephalum,

multinucleated

of numerous

(2,19).

for

and the

substratrum.

14 cm diameter

attractants

we describe

a large

near

chemotactic

or spherulates

the assembly

last

surrounded

the

relayed

a cyclic

centers.

of amaebae

the aggregation

to be one of the known

these

is

the cells

movements

entirely

AMP receptor

receiving

the microplasmodium

coalesce

environment.

only

is

fashion

discodeum,

Myxomycete,

after

AMP mediated

to the aggregation

Dictylstelium studied

cyclic

cyclic

since

The pulsatile

RESEARCH COMMUNICATIONS

The signal

(15,16)

20 urn towards

pseudoplasmodium,

Similar

(12).

immediately

the center.

approximately

between

molecules

rings

a refractory

cleverly

association

phosphodiesterase

waves of expanding

AND BIOPHYSICAL

in p. Not

microplasmodia. plasmodia

also

of a coalesced Cyclic (21). is not

of the

coalesce

plasmodium

AMP has been In this required

or

reported

report, in the

in 2. polycephalum. MATERIALS

AND METHODS

The microplasmodia of p. polycephalum MSC were grown to logarithmic phase in liquid culture with adequate agitation similar to that described in Daniel and Balkwin (2,22). The harvested microplasmodia were washed three times in salt solution and dispersed onto sterile l&mu Millipore circular (pore size: 0.45 urn) laid on the surface of water agar. After approximately 15 minutes, the excess water was removed by absorption into the sunporting agar. Tow of these filter supported microplasmodia were lifted and attached onto a rectangular pre-moistened Millipore filter with one back to back to the other on both sides of the rectangular filter support. The whole support was then allowed to rest on a wire (see legend to the Figure) suspended in a humidity, light and temperature controlled environment such as a screw-cap bottle in a dark room. The microplasmodia on each circular filter coalesced in approximately one hour and the two coalesced plasmodia then migrated as two individuals. The migration pattern of these two plasmodia were observed at half hour intervals.

994

BIOCHEMICAL

Vol. 84, No. 4, 1978

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

RESULTS AND DISCDSSION Chemotaxis, motile

positive

organisms

transduced

(23-28).

auxillary

its

effect

originates

the

including

acrasins folic

are

step

readily

--P polycephalum

dispersed one hour

pseudopodia.

migrate

a time

pattern

impose

period

there

is

any)

microplasmodia

layers do not

states sensitive

observation

to its

individuals acrasin;

in the

entire

that

function

This

as that

these

even molecules,

weight

products

coalesced

afterwards

On

expect

that

molecules

in

both

plasmodia

Our observation

(the

did

of

by sending

on each other.

7 hour

migra-

the patterns which

super-

are diffusable

and one rectangular documented

a

signallers.

filter

was recorded

filters

is

the microplasmodia

we would

small

recognized

disposed.

study,

In -NO instance

suggests

in Acrasiales

filter

support,

in inducing

coalescence.

used in this

the possibility

of both

Figure).

to

chemotaxis

molecular

migration

10 hours

(2 circular

or plasmodia

The plasmodia eliminating

This

that

(12),

Millipore

superimpose

than

commonly

communication

in this

and

related

In general,

small

for

operating,

they

longer

was shown in the

the three

is

that

are

independent

chemotaxis

on each other.

through if

If

described

and began

the idea

specific

quality

on each circular

in such a pattern

throughout tion

support

has been

been

is

chemoreceptor

strictly

of Aerasiales.

AMP and others a good

as the

to amaebae aggregation.

are species

diffusable, filter

which

in many

the chemoreception

and not

has never

in morphogenesis

cyclic

the rectangular

approximately

leads

(attractants)

acid,

(such

(23,24),

usefulness

chemotaxis

initial

though

repel

observed

that

chemotaxis)

and toxicants

In Acrasiales,

system

of the organism,

from physiological

significant

of the finding

in bacterial

on the physiology attract

has been widely

chemotactic

components

as nutrients

out

In spite

by a specialized

its

which

and negative,

that (29). the

study

noncoalescence

is

In Acrasiales,

formed

period

comes from

995

the

same culture,

due to different

only

pseudoplasmodia

(including

the

the amaebae is

not

coalescence

(1,30).

thus physiological state

is

The

from microplasmodia)

Vol. 84, No. 4, 1978

BIOCHEMICAL

AND BIOPHYSICAL

RESEARCH COMMUNICATIONS

Microplasmodia on each circular filter coalesced to give two separate small plasmodia migrating on both sides of the Millipore support. The migrating pattern of one plasmodium seven hours after set-up was shown on the left hand panel and that of both plasmodia were revealed by the opposite panel. Left hand panel: illumination from top; right hand panel: illumination from bottom.

showing

definitely

superimposably, however, not

no instance does not

support

an extracellular

explain

This

the nonsuperimposed

to the back

was observed

phosphodiesterase due only

in all is

to cyclic

coalescence

in contact

(30).

It

it

filter,

experiments

indeed

pattern

(31); of the

one of the plasmodia

of the

that

responsible

in the is apparent

-did

for

that

case

coalescence.

996

not

plasmodia around

the one on the back. If

both

is,

enzyme should

to migrate

with

observed

is

this

the extracellular

chemotaxis,

even though

chemotaxis

but

There

two separate

attempted.

have

migrate

event.

allowed

inhibiting

we should latter

is

coalesce

were

plasmodia

chemotaxis

reported

migration

if

to back

a state-dependent

AMP attractant,

inhibiting

the back

phosphodiesterase

as shown by the following: the support

whereby

presumably

the same enzyme individuals

required

for

were plasmodial

vol. 84, No. 4, 1978

BIOCHEMICAL

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

ACKNOWLEDGEMENTS This

research

was partially

supported

by University

of Hong Kong Research

Grant. REFERENCES 1. 2. 3. 4. 5. 6. 7. a. 9.

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.

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997

Chemotaxis: not a prerequisite for plasmodia coalescence in Physarum polycephalum.

BIOCHEMICAL Vol. 84, No. 4, 1978 AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages October 30,1978 : NOT A PREREQUISITE CHEMOTAXIS 993-997 FOR PLAS...
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