The maize transcription factor Sn alters proanthocyanidin synthesis in transgenic Lotus corniculatus plants

Abstract

Lotus corniculatus L. plants were transformed with Agrobacterium rhizogenes binary vector carrying the maize Sn regulatory gene driven by the 35S promoter. These plants showed modifications in the pattern of accumulation of proanthocyanidin (PA). All the transformed plants but one showed an increase in PA content in the root relative to control untransformed and control gus gene transformed plants (C). With respect to the PAaccumulation in leaves, Sn transgenic plants were grouped in two classes: suppressed (S), that showed a consistent reduction of foliar PAcontent, and unsuppressed (U) that did not differ significantly from controls. Dihydroflavanol reductase (DFR) and leucocyanidin reductase (LAR) enzyme activities in S and U plant leaves mirrored the changes seen with foliar PA accumulation. LAR activity in the roots was consistent with the root PA levels. Mature Sn mRNA accumulated in the leaves of U plants, but not in leaves of S plants; however, leaves of both S and U plants were able to initiate Sn transcription. All Sn-transformed plants accumulated Sn message in root tissue. A possible negative interaction of Sn and an unidentified homologous endogene is proposed for explaining the behaviour of S plants.