Disruption of Brachypodium lichenase alters metabolism of mixed‐linkage glucan and starch

SUMMARY Mixed‐linkage glucan, which is widely distributed in grasses, is a polysaccharide highly abundant in cell walls of grass endosperm and young vegetative tissues. Lichenases are enzymes that hydrolyze mixed‐linkage glucan first identified in mixed‐linkage glucan‐rich lichens. In this study, we...

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Published in:The Plant journal : for cell and molecular biology 2021-11, Vol.109 (4)
Main Authors: Fan, Mingzhu, Jensen, Jacob K., Zemelis‐Durfee, Starla, Kim, Sang‐Jin, Chan, Jia‐Yi, Beaudry, Claudia M., Brandizzi, Federica, Wilkerson, Curtis G.
Format: Article
Language:English
Subjects:
BASIC BIOLOGICAL SCIENCES
BdLCH1
Brachypodium distachyon
chlorenchyma cells
lichenase
mixed-linkage glucan
starch
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Summary:SUMMARY Mixed‐linkage glucan, which is widely distributed in grasses, is a polysaccharide highly abundant in cell walls of grass endosperm and young vegetative tissues. Lichenases are enzymes that hydrolyze mixed‐linkage glucan first identified in mixed‐linkage glucan‐rich lichens. In this study, we identify a gene encoding a lichenase we name Brachypodium distachyon LICHENASE 1 ( BdLCH1 ), which is highly expressed in the endosperm of germinating seeds and coleoptiles and at lower amounts in mature shoots. RNA in situ hybridization showed that BdLCH1 is primarily expressed in chlorenchyma cells of mature leaves and internodes. Disruption of BdLCH1 resulted in an eight‐fold increase in mixed‐linkage glucan content in senesced leaves. Consistent with the in situ hybridization data, immunolocalization results showed that mixed‐linkage glucan was not removed in chlorenchyma cells of lch1 mutants as it was in wild type and implicate the BdLCH1 enzyme in removing mixed‐linkage glucan in chlorenchyma cells in mature vegetative tissues. We also show that mixed‐linkage glucan accumulation in lch1 mutants was resistant to dark‐induced degradation, and 8‐week‐old lch1 plants showed a faster rate of starch breakdown than wild type in darkness. Our results suggest a role for BdLCH1 in modifying the cell wall to support highly metabolically active cells.
ISSN:0960-7412
1365-313X