An easy relationship between a beetle and its yeast symbiont

Date:
December 10, 2021
Source:
Nagoya University
Summary:
Lizard beetles farm yeast inside bamboo stems for their developing
larvae to eat. Scientists have now found that, contrary to other
insect-fungus relationships, the job of the yeast in this one does
not involve digesting the complex sugars in bamboo's woody tissues
for its host.



FULL STORY ========================================================================== Japanese lizard beetle larvae feed on yeast injected from their mothers' abdomens into the bamboo stems they are growing in. Now, scientists at
Nagoya University have made a surprising discovery: the yeast can digest
some complex sugars in the bamboo woody tissue, but it doesn't. Instead,
it consumes much simpler and more available sugar sources.


========================================================================== "This was a real surprise," says Nagoya University bioagricultural
researcher Wataru Toki. "While yeast can indeed decompose those
indigestible components, our analysis shows the yeast actually grows
on small molecule monosaccharides." The results are published in the
journal Scientific Reports.

Female Japanese lizard beetles carry the yeast Wickerhamomyces anomalus in
a specialised pocket-like organ. In spring, they dig holes in bamboo and
insert their eggs and the yeast. W. anomalusgrows into a sort of fungal
garden that the very hungry beetle larvae munch on as soon as they hatch.

In other symbiotic relationships, fungi typically break down complex
sugars into more digestible chunks that their host insects can feed
on. Toki and his colleague, Dan Aoki, wanted to know whether this was
also the case in the relationship between the Japanese lizard beetle
and W. anomalus.

Their research suggests not. The scientists used a technique called
ion exchange chromatography to analyse and compare the sugar content
of fresh bamboo pith, and pith colonized by yeast alone or by yeast and
beetle larvae.

The comparison revealed that the yeast mostly ate the simple free sugars glucose and fructose.

This surprised the scientists because further tests showed that the
yeast can actually digest some complex, indigestible sugars if necessary.

"Bamboo is not only a farm for the yeast but also a house for the
larvae. So the larvae can live in a strong house safely because the
house is not decomposed by the food," explains Toki.

The researchers now want to further investigate the relationship. Perhaps,
they suggest, the beetle larvae grow larger inside unusually sweet bamboo, giving them a competitive advantage. The scientists also want to know
how adult females distinguish free-sugar-rich bamboo to lay their eggs.

========================================================================== Story Source: Materials provided by Nagoya_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Wataru Toki, Dan Aoki. Nutritional resources of the yeast symbiont
cultivated by the lizard beetle Doubledaya bucculenta in bamboos.

Scientific Reports, 2021; 11 (1) DOI: 10.1038/s41598-021-98733-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211210103152.htm

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