Cloning of Chalcone Synthase Gene GhCHS1 and Its Function Analysis in Coloured Cotton (Gossypium hirsutum)
LIANG Xian-Li, ZHANG Li-Qing, KE Li-Ping, SUN Yu-Qiang*
Laboratory of Plant Genome and Coloured Fiber Molecular Improvement, Key Laboratory of Plant Secondary Metabolism and Regulation of Zhejiang Province, School of Life Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, China
Abstract：The chalcone synthase gene (CHS) were the first committed enzyme gene of flavonoid biosynthesis, CHS condensed 3 molecules of malonyl-CoA and 1 molecule of p-coumaroyl-CoA to form naringenin chalcone. The study was to investigate the relationship between GhCHS1 gene and the formation of fiber color through virus induced gene silencing (VIGS) in colored cotton ZongXu1 (Gossypium hirsutum). The expression of GhCHS1 gene in interference lines (GhCHS1i) was measured by qRT-PCR, and the anthocyanins contents in the fibers and seedcoat, leaves and cotton kernels were determined. Bioinformatics analysis indicated that GhCHS1 proteins were mainly distributed in vacuoles, and the secondary structure of GhCHS1 proteins was mainly composed of random coil and alpha helix. 24 CHS members were screened in the known genomes of Gossypium, belonging to 7 types according to homology, and 6 types of tertiary spatial structures. GhCHS1 (GenBank No. LOC107897841) was predominantly expressed in the developing fibers and leaves of Zongxu1. The expression of GhCHS1 gene was increased in the early developing fibers (0~9 DPA, day post anthesis), reached the peak at 9 DPA, and then decreased from 12 DPA to 20 DPA. The GhCHS1 gene was interference by VIGS technology, and a large number of transgenic interference lines were obtained. Phytoene desaturase (GhPDS) was silenced by VIGS as the positive control, vector-empty CK was used as the negative control, and Zongxu 1 WT was used as the wild type control. The GhCHS1i lines had slightly curly leaves the same as the phytoene desaturase gene interference (GhPDSi) and vector-empty plants compared with the WT plants. The GhCHS1 expression level was significantly decreased in the GhCHS1i plants, the fiber color of GhCHS1i plants was significantly lighter compared with the brown fiber of WT Zongxu1, and different from the white fiber of upland cotton C312. The expression level of GhCHS1 gene in the developing fibers of GhCHS1i lines was significantly lower than that in the WT, the fiber color of the GhCHS1i lines was lighter brown. The expression level of GhCHS1 gene was indicated the positive correlation with the fiber color. Compared with the WT, the GhCHS1i lines had the lower the expression level of GhCHS1 gene, the fiber color appeared significantly lighter (P<0.05). The analysis of anthocyanin content showed that the less the anthocyanin content of fiber and seed coat, cotton kernel, the fiber color became significantly lighter. The results indicated that GhCHS1 gene was involved in the biosynthesis and accumulation of anthocyanins in colored cotton leaves, fiber and seed coat, cotton kernel, and also played an important role in the fiber pigmentation. This study would have important reference value for the formation mechanism of fiber color formation in colored cotton.
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