Study On A Cytochrome P450Gene SbCYP From Sorghum Bicolor

Fossil energy is running out, and the problem of energy structure and supplement gets worse, which urge us to research new environmentally friendly, reproducible, efficient and fungible energy. Bio-energy is one of the most promising new energy resources, among which cellulosic ethanol is the most potential, ideal and sanitary energy resource. Therefore, to develop lignocellulosic bio-energy is meaningful to remit the over-dependence on fossil energy in China. Cellulose, the most widespread biomass around the world, is the most important raw material for bioethanol production. Sorghum bicolor has large amount of biomass, and it possesses superior resistance to salt and alkali, drought, and infertility so that it can grow well in the low-quality soils. Therefore, sorghum becomes one of the most crucial sources of lignocellulose. It is a feasible strategy in lignocellulose conversion to lower the lignin content in plant cell wall or to change the proportion of G/S lignin, because this can drastically increase the production efficiency of cellulosic ethanol, reduce the production cost, improve economic performance, and consequently make the cellulosic ethanol industry more practicable. Hence, to elucidate the regulatory mechanisms underlying the lignin biosynthesis and metabolism will help to improve bio-energy plants through genetic manipulation and promote the cellulosic ethanol industry.SbCYP (Sb02g030640.1) of S. bicolor is a CYP78member of cytochrome P450gene family, and its function is unknown so far. In this study, we found that SbCYP over-expressed Arabidopsis thaliana exhibited higher plants and early flowering, while the mutant of AtCYP78A9, the homologue in A. thaliana lowered the plants but had no effect on flowering. SbCYP altered the transcription of several flavonoid synthesis associated genes via affecting the activity of MYB75. The over-expression of SbCYP increased the grain weight and the number of siliques in stalk, delayed seed germination. SbCYP over-expression participated in the plant photomorphogenesis, where the cotyledon etiolation was promoted in the dark, and the cotyledon was enlarged and opened earlier in the light. SbCYP lowered the resistance to oxidative stresses, and the growth of its over-expression lines was more pronounced under the treatment of0.5mMH2O2. SbCYP promoted lignin biosynthesis, and SbCYP overexpression lines had higher lignin content and superior conversion efficiency of cellulosic ethanol. Therefore, SbCYP appears to have diverse effects on plant growth and development (plant height, silique and seed et al.), morphogenesis (cotyledon), secondary metabolism (flavonoid and lignin) and abiotic stress tolerance (oxidation tolerance).SbCYP shares high similarities to the homologues of monocots, including a P450member of Zea mays (87%), a CYP78A3-like protein of Oryza sativa (87%), and a CYP78A3-like protein of Brachpodium stachyon (79%), the latter two proteins possess a conservative ferulic acid5-hydroxylase(F5H) domain. SbCYP shares61%identity with CYP78A9, the most homologue in A. thaliana, but CYP78A9may not have F5H activity. In order to explore the association between SbCYP, AtCYP78A9and F5H, we obtained the homologous T-DNA insertion mutants of AtCYP78A9and AtF5H. We cloned three putative F5H genes (Sb01g017270, Sb02g002630, SbCYP) from S. bicolor, and constructed their A. thaliana overexpression lines. We further transformed SbOlg017270, Sb02g002630, SbCYP into AtF5H mutant and SbCYP into AtCYP78A9mutant to know whether they can complement the function of the homologues of A. thaliana.Besides, our lab previously identified a transcription factor gene SbbHLH1from Sorghum bicolor, and its overexpression in A. thaliana drastically inhibited lignin synthesis. In order to know whether this gene can perform this function in bio-energy plants, in this study, we transformed SbbHLHl into Populus tomentosa by the Agrobacterium infection method. We have obtained ten positive transgenic lines, and the transgene was confirmed to stably integrate in the genome of P. tomentosa and describe in the transgenic plants. We propose to measure the effect of SbbHLHl on lignin synthesis and plant development, to primarily know the potential of this gene in the molecular breeding of bio-energy plants with low lignin.