Gene Expression And Photosynthesis Change In Wheat Spike Under Water Deficit

Drought is the most important factor to limit wheat production around the world. It is reported that, spike organs of wheat performed significantly photosynthetic advantages and grain-fling contribution than leaves under drought condition. It is important for both theoretical and practical meanings to research physiological and molecular mechanism of drought resistance involved in wheat ear. In this study, drought-resistant cultivator Pubing143 and water-sensitive one Zhengyin1 were used as the material and pot experiment were performed. Transcriptional expression of glume, net photosynthesis and chlorophyll content of ear were detected, and yield traits were also counted. The main results were listed as follow:1. We investigated variations of gene expression of glume in Zhengyin 1 at 6 d after anthesis(DAA by using Affymetrix Wheat Genome Array. 566 differentially expressed probe sets were identified. A total of 477 genes were up-regulated(FC≥2.0) and 89(FC≤0.5) were down-regulated under water deficit. Most up-regulated genes were involved in functions such as cell, cell part, macromolecular complexes and metabolic process. Among these up-regulated genes, we identified signaling proteins, transcription factors, and abiotic stress-related genes. The signal pathway networks constructed with KEGG showed three important genes involved in the phenylalanine metabolism, in which phenylalanine ammonialyase, cinnamic acid hydroxylase, chalcone synthase, and chalcone isomerase located at the center of the pathway, which indicated their pivotal roles in the phenylalanine metabolism and flavonoid biosynthesis derived from carbohydrate metabolism.2. Ear net photosynthesis of both wheat cultivars were increased and then dropped during whole grain filling process under different water supply, and reached peak at 10 day after anthesis(DAA). At the early grain-fling period(DAA6), compared with well-water supply group, net photosynthesis in ear of drought-resistant Pubing143 increased by 10.64%(P<0.05) while decreased in drought-sensitive Zhengyin1 by 26.12%(P<0.05) under water deficit. Pn in Pubing143 spike(P<0.05) dropped significantly at 10 and15 DAA, and markedly reduced in Zhengyin1(P<0.01).Chlorophyll content, transpiration rate and relative water content decreased slightly in Pubing143(P>0.05) while significantly decreased in Zhengyin1(P<0.05).It is suggested that effect of water deficit on water-sensitive Zhengyin 1were more significantly, especially at the early and middle grain filing period.3. Under water deficit, yield trait and harvest index(HI) of water-sensitive Zhengyin 1 dropped strikingly by 40.2% and 14.0%(P<0.05) respectively, while slightly decreased in drought-resistant Pubing143. Thousand grain weight of Pubing143 and Zhengyin 1 decreased significantly(P<0.05) by 5.26% and 12.44% respectively; The drop scale of thousand grain weight in Pubing143 is less than that in Zhengyin 1.Under water deficit, water use efficiency(WUE) of Puing143 increased by 5.43%(P<0.05) while decreased by 16.21%(P>0.05) in Zhengyin1.It can be conclude that effect of moderate water deficit on drought-resistant wheat yield is limited, and WUE improved.