摘要
摘要:为了揭示高表达转玉米C₄-磷酸烯醇式丙酮酸羧化酶（PEPC，EC 4.1.1.31）基因水稻（PC）在耐旱中光合与花青素调节途径的内在联系，本研究以PC和未转基因野生型原种（WT）的水培苗为试验材料，在4~5叶期，通过50 μmol·L-1光合抑制剂DCMU[3-（3'，4'-dich-lorophenyl）-1，1-dimethyl-urea]预处理1 h，观察其在12% PEG-6000模拟干旱处理下的表现。结果表明，在模拟干旱条件下，DCMU预处理使两种供试材料相对含水量显著下降，且PC相对含量显著高于WT；干旱处理下，两种材料的花青素含量显著升高，DCMU和干旱处理使两种材料的花青素含量下调，且PC水稻中始终伴随着较高的花青素含量。光合数据表明，与单独12% PEG-6000处理相比，DCMU联合12% PEG-6000处理显著抑制了两种水稻材料的净光合速率、气孔导度、胞间CO₂含量及羧化效率，但PC的各指标显著高于WT。同时，DCMU联合12% PEG-6000处理显著下调两种供试材料的内源蔗糖含量，但PC中蔗糖含量显著高于WT。进一步研究发现PC中更高的蔗糖含量与花青素合成有关转录因子bHLH（OsB1，OsB2）、R2R3-MYB（OsC1）、COP1（constitutively photomorphogenic 1）、HY5（elongated hypocotyl 5）更高的转录水平同步，下游花青素合成相关基因OsPAL、OsCHI、OsCHS、OsF3H、OsF3'H、OsDFR、OsANS的表达量增加。PC水稻可能通过诱导NO和Ca²⁺感受干旱信号，参与转录因子的调节，进而参与花青素合成基因的调控，合成较多的花青素，增强PC水稻对干旱逆境的响应，增强保水能力，最终表现耐旱。
Abstract:Anthocyanins are important antioxidant materials that protects plant from damage by reactive oxygen species (ROS). Especially under adverse conditions, the regulation of sucrose in plants depends on its ability to induce anthocyanin accumulation. To determine the intrinsic relationship between photosynthetic and anthocyanin regulated pathways for C₄-phosphoenolpyruvate carboxylate (PEPC, EC 4.1.1.31) gene overexpressed rice (PC) in drought conditions, PC and untransformed wild-type (WT) were treated with 50 μmol·L-1 photosynthetic inhibitor DCMU for 1 h and the performance of the rice seedlings at 4-5 leaf stage observed under 12% PEG-6000 simulated drought. The results showed that DCMU pretreatment significantly reduced relative water contents of WT and PC under simulated 12% PEG-6000 drought condition, and relative water content of PC was significantly higher than that of WT. The anthocyanin content was higher in PC than in WT under 12% PEG-6000 simulated drought or drought plus DCMU pretreatment. 12% PEG-6000 simulated drought decreased anthocyanin contents of PC and WT, while DCMU pretreatment alleviated this effect. Compared with 12% PEG-6000, DCMU plus 12% PEG-6000 significantly inhibited net photosynthetic rate, stomatal conductance, intercellular CO₂ and carboxylation efficiency of the two rice lines, but these parameters of PC lines were significantly higher than those of WT lines. Then DCMU plus 12% PEG-6000 down-regulated endogenous sucrose content of the two materials, but sucrose content of PC lines was significantly higher than that of WT lines. Further studies showed that higher sucrose level in PC was associated with higher expression levels of transcriptional factors of bHLH (OsB1, OsB2), R2R3-MYB (OsC1), COP1 (constitutively photomorphogenic 1), HY5 (elongated hypocotyl 5), OsPAL, OsCHI, OsCHS, OsF3H, OsF3'H, OsDFR and OsANS, which resulted in synthesizing more anthocyanin to improve water retention capacity. In addition, PC rice sensed drought signals through NO and Ca²⁺, which participated in the regulation of transcription factors, regulation of anthocyanin synthesis gene, synthesis of more anthocyanin and thereby enhanced PC rice response to drought stress. This enhanced water retention capacity, stabilized photosynthetic capacity and resisted drought. Therefore, it was beneficial in molecular breeding of "C₄ Rice" to study the symphony between high yield and plant resistance.



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