A mutant deficient in S-adenosylhomocysteine hydrolase in Arabidopsis shows defects in roothair development

Abstract

Root-hair development is a process involving the interplay between genetic, hormonal, and environmental factors. An Arabidopsis mutant, referred to as sahh1, was initially recovered from a screen for delayed germination. Molecular characterization of the sahh1 mutant revealed that it contained a T-DNA insertion 82 bp 5′ to the coding sequence of S-adenosylhomocysteine hydrolase 1 (SAHH1, At4g13940), resulting in the reduction of SAHH1 expression. The resulting reduction in expression of SAHH1 produced plants with short, hairless roots, delayed germination, and slow growth. All of these phenotypes were restored to normal by complementing the sahh1 mutant with a full length cDNA. In plants, SAHH1 converts S-adenosylhomocysteine to homocysteine in the activated methyl cycle, and is a precursor for methionine and Sadenosylmethionine. Using the root hairless phenotype of the sahh1 mutant as a visual assay, the effects of SAHH1 deficiency on the synthesis of homocysteine, S-adenosylmethionine, 1-cyclopropane-1-carboxylic acid, and spermidine were investigated.