外源葡萄糖增强高表达转玉米C_4型pepc水稻耐旱性的生理机制

Physiological Mechanism on Drought Tolerance Enhanced by Exogenous Glucose in C_4-pepc Rice

为揭示葡萄糖参与植物耐旱性的内在机制,以高表达转玉米C4型磷酸烯醇式丙酮酸羧化酶(phosphoenolpyruvate carboxylase,PEPC)基因(C4-pepc)水稻(PC)和受体"Kitaake"(WT)为材料,通过盆栽和水培试验,研究外施葡萄糖联合干旱处理下,功能叶片的光合参数、总可溶性糖及其组分、Ca2+、NO含量、己糖激酶活性、B类钙调磷酸酶(calcineurin B-like,CBL)与蔗糖非发酵1(sucrose nonfermenting-1,SNF1)相关蛋白激酶(SNF1-related protein kinase 3s,Sn RK3s)基因表达的变化。结果表明,在盆栽试验中,分蘖期外施3%葡萄糖联合干旱处理对水稻的产量及其构成因子影响不显著,而在孕穗期处理,PC的株高、穗数、每穗实粒重和单株产量均显著高于WT。在水培试验中,外施1%葡萄糖和12%(m/v)聚乙二醇6000(polyethylene glycol-6000,PEG-6000)模拟干旱处理,均显著提高了PC功能叶片的净光合速率(Pn)、气孔导度(Gs)和羧化效率(CE),叶片内蔗糖和果糖的含量也均显著高于WT。值得关注的是,PC叶片己糖激酶(hexokinase,HXK)活性、CBL1/Sn RK3.1/Sn RK3.4/Sn RK3.21基因的相对表达量在外施1%葡萄糖联合12%PEG模拟干旱处理下均显著低于12%PEG处理,而NO含量则显著上升。相关性分析也表明,PC中Pn、胞间CO2浓度(Ci)和Gs分别与葡萄糖含量、HXK活性和Sn RK3.16基因表达显著相关。外施葡萄糖处理可上调PC糖水平,下调其CBL和Sn RK3s基因表达,诱导NO参与叶片气孔调节,从而增强保水能力,保持光合能力稳定,最终表现为耐旱。

In order to investigate the intrinsic mechanism of glucose participated in drought tolerance in plants,the effects of glucose were studied using the phosphoenolpyruvate carboxylase(C4-pepc)rice(PC)and“Kitaake”(WT)rice lines in pot experiments and hydroponics experiments respectively.The changes of photosynthetic parameters,total soluble sugar and sugar componentscontents,Ca2+and NO contents,hexokinase activity,transcript levels of sucrose nonfermenting-1(SNF1)-related proteinkinases3(SnRK3s)and calcitonin B-like(CBL)of the functional leaves in rice lines were measured.Agronomic traits of the wild type(WT)and PC were recorded in the mature period.In pot experiment,the treatment of3%glucose with drought during tillering stage had no significant effect on agronomic traits of the tested rice.During the booting stage,the plant height,panicle number per plant,filled grain number per panicle and grain yield per plant in PC were significantly higher than in WT(P<0.05).In the hydroponics experiment with1%glucose combined with12%(m/v)polyethylene glycol6000(PEG-6000)to simulate drought stress,the photosynthetic parameters such as net photosynthetic rate(Pn),stomatal conductance(Gs)and carboxylation efficiency(CE)significantly increased in PC than in WT.Similarly,the contents of sucrose and fructose of leaves in PC lines were significantly higher than those in WT.It was noteworthy that hexokinase(HXK)activity and the relative gene expression of CBL and SnRK3.1/SnRK3.4/SnRK3.21in PC lines under the treatment with1%glucose and12%PEG were significantly lower than those under12%PEG treatment alone.Intriguingly,the NO contents of PC under the corresponding treatments were significantly increased(P<0.05).In addition,the photosynthetic parameters were significantly correlated with the glucose content,HXK activity and SnRK3.16transcript level respectively in PC lines.It is suggested that PC can decrease the expression of CBL and SnRK3s gene by increasing glucose,participate the stomatal regulation via NO,maintain relative water content,keep stable photosynthetic capacity,and therefore confer drought tolerance.