Expression of a chimeric GUS gene construct as a tool to study nodule morphogenesis in chicory leaves

Leaves from micropropagated chicory plantlets were cultivated in vitro to r egenerate organogenic nodules. The nodules were transformed with a 2.3 kb f ragment of an apple calmodulin promoter region fused to the coding sequence of uidA reporter gene. Histochemical detection of beta -glucuronidase expr ession in transgenic regenerants showed that vessel-associated cells were s trongly stained. Previous histological investigations have shown that the d ifferentiation of vascular elements is essential to nodule and bud-derived- nodule development. Therefore, beta -glucuronidase activity was tested in a single transgenic chicory line during nodule morphogenesis and bud regener ation. The vascular connections between leaves and nodules, then between no dules and buds were stained blue, indicating an alternative system for dete rmining the histological origin of nodules and adventitious buds from chico ry leaf explants.