Regulated expression of ADPglucose pyrophosphorylase and chalcone synthase during root development in sweet potato

The phase transition in sweet potato root during tuber differentiation is a complex developmental process that involves changes in gene expression and morphogenesis. Among the three kinds of root in sweet potato (white fibrous root, thick-pigmented root and lateral root), ADP-glucose pyrophosphorylase (AGPase) and chalcone synthases (CHS) are expressed only in thick-pigmented roots after 3 weeks, and this also depends on the developmental stage. Since exposing roots to the light or culturing under hydroponic conditions inhibits tuber formation in sweet potato, the expression of AGPase and CHS was studied under light and dark conditions. AGPase and CHS expression in sweet potato roots was suppressed very sensitively by light or water stress, similar to root developmental patterns. Based on an analysis of AGPase and CHS expression in different kinds of root tissues and in different developmental stages, these genes were shown to be closely associated with the differentiation of thickening pigmented roots.