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Flavonol rhamnosylation indirectly modifies the cell wall defects of RHAMNOSE BIOSYNTHESIS 1 mutants by altering rhamnose flux
Author(s) -
Saffer Adam M.,
Irish Vivian F.
Publication year - 2018
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13885
Subject(s) - rhamnose , cotyledon , mutant , arabidopsis , petal , arabidopsis thaliana , cell wall , biology , polysaccharide , biochemistry , microbiology and biotechnology , botany , gene
Summary Rhamnose is required in Arabidopsis thaliana for synthesizing pectic polysaccharides and glycosylating flavonols. RHAMNOSE BIOSYNTHESIS 1 ( RHM 1 ) encodes a UDP ‐ l ‐rhamnose synthase, and rhm1 mutants exhibit many developmental defects, including short root hairs, hyponastic cotyledons, and left‐handed helically twisted petals and roots. It has been proposed that the hyponastic cotyledons observed in rhm1 mutants are a consequence of abnormal flavonol glycosylation, while the root hair defect is flavonol‐independent. We have recently shown that the helical twisting of rhm1 petals results from decreased levels of rhamnose‐containing cell wall polymers. In this study, we found that flavonols indirectly modify the rhm1 helical petal phenotype by altering rhamnose flux to the cell wall. Given this finding, we further investigated the relationship between flavonols and the cell wall in rhm1 cotyledons. We show that decreased flavonol rhamnosylation is not responsible for the cotyledon phenotype of rhm1 mutants. Instead, blocking flavonol synthesis or rhamnosylation can suppress rhm1 defects by diverting UDP ‐ l ‐rhamnose to the synthesis of cell wall polysaccharides. Therefore, rhamnose is required in the cell wall for normal expansion of cotyledon epidermal cells. Our findings suggest a broad role for rhamnose‐containing cell wall polysaccharides in the morphogenesis of epidermal cells.