Suppression of α-l-arabinofuranosidase in the endosperm and atypical germination of lettuce seeds induced by sodium dichloroisocyanurate

Abstract

Endosperm cap (CAP) weakening and radicle (RAD) elongation growth are prerequisites for the completion of lettuce seed germination. Lettuce CAP and RAD cell walls contain a large amount of l-arabinofuranose, which may exist in the form of arabinan or l-arabinofuranose-rich polysaccharides. The aim of the present study was to investigate the relationship between α-l-arabinofuranosidase, an enzyme degrading l-arabinofuranose-rich polysaccharides, and CAP weakening and RAD elongation growth. It was shown that the enzyme activity and the transcript abundance of two lettuce α-l-arabinofuranosidase genes, LsARAf2 and LsARAf7, increased in the CAP and RAD prior to the completion of seed germination during imbibition in water. Sodium dichloroisocyanurate, a chemical inducing atypical germination (RAD elongation without endosperm rupture) in lettuce seeds, significantly decreased the enzyme activity and the transcript abundance of LsARAf7 and LsARAf2 in the CAP. It is concluded that the expression of α-l-arabinofuranosidase is necessary for CAP weakening and the suppression of this enzyme in the CAP is at least partly responsible for atypical germination in lettuce.