Exploration of substrate diversity of Leucoanthocyanidin Reductases (LAR).

Proanthocyanidins (PAs) are mainly composed of epicatechin (EC) or catechin (C) subunits. C-type catechins (C and GC) are generally considered to be catalyzed by Leucocyanidin reductase (LAR). In this study, we re-evaluated the function of LAR. LcLAR1 was isolated from Lotus corniculatus that is rich in C-type catechins. Overexpression of LcLAR1 in tobacco resulted in a significantly increased content of EC and EC-glucoside. Overexpression of LcLAR1 in Arabidopsis thaliana promoted the accumulation of soluble PAs, including EC, PA-dimer and PA-trimer. However, in transgenic ans mutant overexpressing LcLAR1, the contents of C and C-glucoside were increased. In addition, overexpression of LcLAR1 in Lotus corniculatus resulted in a significant increase of C levels. Taken together, the products of LcLAR1 depended on the substrates, which revealed the substrates diversity of LcLAR1. Our study provides new sights into flavonoid pathway, especially the role of LAR.