Orange Montastrea cavernosa recruits?

[Mikhail Matz]

    Dear Dr. Murray,
    thank you very much for your posting. So, here comes the reasoning
against photoprotection function of fluorescent pigments from corals.
These pigments are (in the majority of cases) proteins homologous to
green fluorescent protein (GFP) from Aequorea victoria, as we recently
found out  (Matz et al, Nat.Biotechnol. 17: 969-973, 1999).
    We already had a bit of this discussion with prof. Ove
Hoegh-Guldberg of the University of Queensland (oveh at uq.edu.au), who was
also suggesting photoprotection as the major role of fluorescent
proteins. Here is a part of what I wrote to him directly in responce:

Concerning photoprotection I would rather disagree with you. First of
all, corals possess a multitude of low-molecular sunscreen
compounds for this purpose (see, for example, Dunlap, W.C. et al.
Nature's sunscreen from the Great Barrier Reef, Australia. International
Journal of Cosmetic Science 20, 41-51 (1998)), so additional recruitment
of specialized proteins
for the same purpose seems rather tedious. Still, if it still was
protection from UV, there is no difference which
fluorescent color to use - green or red, they are both UV-excitable.
Meanwhile, our most recent data on molecular features of red-emitters
suggest that they are advanced versions of greens, so that a point
mutation would most likely damage
the red protein making it green. Therefore, red color should have some
special role in nature (different from green!)
to be maintained by natural selection, otherwise all the red-emitters
would have long since deteriorated into greens due to mutation pressure.
In addition, red-emitters are heavily suboptimal in comparison to greens
in terms of photoprotection - they all have much lower quantum yields of
fluorescence.

    So, I think that the coral fluorescence file is still far from being
closed.
    I would be happy to continue this discussion, especially taking in
account that the question of the fluorescent proteins function in corals
is exactly the subject of my current research.

sincerely yours

Mikhail Matz, Ph.D.
Institute of Bioorganic Chemistry
Miklukho-Maklaya 16/10
117871 Moscow, Russia
 

Robert Murray wrote:

> Hi Iain et al, Coral photobiology is not my area of study, although I
> did examine the topic some years ago. I believe it is fairly common
> for many corals to exhibit brightly coloured fluorescence pigments
> (especially those in shallowest water conditions where light intensity
> is greatest). From some of the literature I have read I seem to
> remember a plausible case for these pigments operating as some sort of
> protection against the destructive energy of short (UV) wavelengths,
> by liberating some of this energy as harmless (less energetic) visible
> fluorescence. Perhaps this is one of the discredited theories now. If
> so, I would be interested to hear the evidence against it. Regards to
> all Robert Murray.  (What's up Iain?)  =======================
> ROBERT MURRAY  BSc, FGA,
> Discovery Bay Marine Laboratory,
> Discovery Bay, Jamaica, W.I.
>
> Tel. (876) 973 2946
> Fax. (876) 973 3091
> rmurray at infochan.com
> WWW.DBML.ORG
> ======================= 
>
>      ----- Original Message -----
>      From: Mikhail Matz
>      To: Iain Macdonald ; coral list
>      Sent: Tuesday, July 25, 2000 11:33
>      Subject: Re: Orange Montastrea cavernosa recruits?
>       Hi Iain,
>      we know a little bit what is the substance causing the
>      fluorescence in
>      corals,
>      and observations, measurements and photos were made about
>      this
>      (see http://www.nightsea.com/references.htm for the list of
>      related
>      papers and websites)
>      Moreover, in particular M.cavernosa fluorescence was
>      measured (in situ)
>      by Charles Mazel
>      and is studied by me (in vitro) right now.
>
>      However, so far we have absolutely no clue as to the
>      function of this
>      fluorescence in
>      nature (if we forget for a moment about older hypotheses all
>      of which
>      seem wrong by now),
>      and the subject is my primary interest. Your observation is,
>      as far as I
>      know, the first
>      information which might help to link fluorescence to some
>      aspect of coral
>      ecology. I would be
>      extremely grateful if you could provide some more details on
>      your
>      observations.
>      I would like to ask all coral listers as well - perhaps you
>      saw
>      something like Iain? Anything
>      which could give a hint about the function of fluorescence?
>      Or perhaps I
>      simply missed something
>      in literature?
>      best wishes,
>
>      Mike Matz
>       
>
>      Iain Macdonald wrote:
>
>      > During a recent field trip i noted the following along my
>      transects.
>      >
>      > M. cavernosa recruits (i use the plural as this was seen
>      three
>      > different times), of only one polyp was noted at approx.
>      15-20m depth
>      > to appear to the unaided eye as fluorescent orange. Close
>      by (ie
>      > 10cm away) 5 polyps were the typical olive green colour
>      with this
>      > "day glow" orange colour around its edges. Again a few cms
>      away
>      > larger colonies 20-25 polyps were only olive green. Is
>      this typical
>      > for recruits (i think not) or maybe as a result of some
>      stress
>      > (sediment) stimulus? I was startled to see such colour
>      from this type
>      > of coral and would like to konw of any other observations.
>
>      >
>      > Cheers
>      >
>      > Iain Macd.
>      >
>      > Room E402 John Dalton Extension Building,
>      > Department of Environmental and Geographical Science,
>      > Manchester Metropolitian University,
>      > Chester Street,
>      > Manchester,
>      > M1 5GD
>      > Tel: 0161 247 6234
>      > Fax: 0161 247 6318
>       
>
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