High impact information on RHD1

• We find that ethylene specifically suppresses all visible aspects of the rhd1 phenotype [1].
• Ethylene restores the biosynthesis of galactose-containing xyloglucan and arabinosylated galactan cell wall polymers in rhd1 back to wild-type levels [1].
• The RHD1 isoform is specifically required for the galactosylation of xyloglucan (XG) and type II arabinogalactan (AGII) but is not involved either in D-galactose detoxification or in galactolipid biosynthesis [2].
• We show that REB1 is allelic to ROOT HAIR DEFICIENT 1 (RHD1), one of five ubiquitously expressed genes that encode isoforms of UDP-D-glucose 4-epimerase (UGE), an enzyme that acts in the formation of UDP-D-galactose (UDP-D-Gal) [2].
• The REB1/RHD1 gene belongs to a family of UDP-D-Glucose 4-epimerases involved in the synthesis of D-Galactose (Gal) [3].

Biological context of RHD1

• In Arabidopsis, mutation of RHD1, a UDP-glucose-4-epimerase, causes root-specific phenotypes, including hypersusceptibility to the cyst nematode Heterodera schachtii, increased root hair elongation, decreased root length, and root epidermal bulging [4].
• A time-course analysis of RHD1 transcript levels in wild-type plants treated with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid showed a root-specific downregulation of RHD1 expression by ethylene [4].
• Our findings indicate that rhd1 is altered in its ethylene response and that ethylene signal transduction positively influences plant susceptibility to cyst nematodes [5].

Associations of RHD1 with chemical compounds

• We conclude that RHD1 is a likely target of root-specific negative regulation by ethylene and that loss of RHD1 function results in a heightened sensitivity of root tissues to both ethylene and auxin [4].
• UGE2 strongly and UGE1 and UGE5 lightly supported UGE4 in influencing root growth and cell wall galactose content by affecting galactan content [6].

References