Chalcone synthases (CHS, EC 2.3.1.74) are key enzymes that catalyze the first committed step in flavonoid biosynthesis. In this study, we isolated a chalcone synthase, named NtCHS6, from Nicotiana tabacum.  This synthase shared high homology with the NSCHSL (Y14507) gene and contained most of the conserved active sites that are in CHS proteins.  The phylogenetic analysis suggested that NtCHS6 protein shared a large genetic distance with other Solanaceae CHS proteins and was the most closely-related to an uncharacterized CHS from Solanum lycopersicum.  The expression analysis indicated
that NtCHS6 was abundantly expressed in leaves, especially in mature leaves.  By scrutinizing its upstream promoter sequences, multiple cis-regulatory elements involved in light and drought responsive were detected.  Furthermore, NtCHS6 expression decreased significantly under dark treatment and increased significantly under drought stress.  Our results suggested that NtCHS6 expression exhibited both light responsiveness and drought responsiveness, and might play important roles in ultraviolet protection and drought tolerance.

Vitamin A deficiency has become a worldwide problem. Biofortified foods can potentially be an inexpensive, locally adaptable, and long-term solution to dietary-nutrient deficiency. In order to improve the b-carotene content in maize grain by breeding and minimize vitamin A deficiency, a complete diallel cross was designed with eight inbred lines of maize, and 64 combinations were obtained in this study. The experimental combinations were planted in Yunnan and Sichuan provinces, respectively, with a random complete block design. The b-carotene contents in the grains of the experimental materials were analyzed by high-performance liquid chromatography. Among the tested materials, the effect difference of general combining ability of the b-carotene content was significant; however, the effect difference of the special combining ability and the reciprocal effect were not significant. The b-carotene content of maize grain was not influenced significantly by the cross and the reciprocal cross. There was a significant correlation about the b-carotene content in the maize grains between the F1 and their parents. The combinations with high b-carotene content were obviously influenced by the environment, and the mean value of b-carotene content for the experimental materials planted in Ya’an of Sichuan was higher than that planted in Yuanjiang of Yunnan, with the results being significant at the 0.01 level.