Differential Expressions of Two-Component Element Genes in Rice Under Drought Stress

The objectives of this study were to gain insight into the temporal and spatial expression patterns of two-component system (TCS) genes in rice (Oryza sativa L.) under drought stress and to understand the relationship between TCS gene expression and drought resistance. Using a whole rice genome microarray, the expression profiles of TCS genes of rice lines with different drought resistance were analyzed at various growth stages. The TCS genes showed greatly difference of expression pattern in various organs but in similar patterns in the same tissues at different stages. Genes for type-A response regulator (RR), a negative regulator of cytokinin (CK) signaling, were mostly repressed by drought stress, whereas, genes for type-B RR with an opposite role to type-A RR were mostly induced by drought stress. These changes were supposed to be related to the enhancement of CK signaling under drought stress. This supposition was confirmed by the down regulation of ethylene receptor genes and the cross-talk of hormones under drought condition. The His kinase genes (HK5 and HK3) that are homologous to CK receptor genes (AHK2, AHK3, and CRE1) in Arabidopsis were induced by drought stress. However, HK6 homologous to AHK5 (CK-independent 2, CKI2) was repressed when exposed to drought stress. These results provided further confirmations of the above supposition. In drought resistant introgression lines and IR64, no significant differences of TCS gene expression profiles were observed under drought stress. This result indicates that the TCS genes are probably in relation to drought responsiveness.

摘 要利用全基因组表达芯片, 系统分析干旱胁迫条件下水稻双组分信号系统(two component system, TCS)相关基因在其不同发育阶段、不同组织以及抗旱能力不同的株系中的表达谱变化特征。结果表明, 双组分信号系统基因在干旱胁迫环境下的表达具明显的时空特异性, 表现为不同组织的TCS基因干旱胁迫表达谱差异较大, 而同一组织内表达谱相似, 其中生殖生长期(幼穗分化期和孕穗期)两个叶片材料中TCS基因表达谱最为接近; 与细胞分裂素信号传导负向调控相关的A型应答调控器在旱胁迫下表达下调, 而与CK信号传导正向调控相关的B型应答调控器呈现明显上调趋势, 推测与干旱胁迫下CK信号传导增强有关, 同时乙烯受体基因在干旱胁迫环境下的表达下调, 从激素间相互关系的角度更好地印证了上述推测; 与拟南芥细胞分裂素受体基因(AHK2、AHK3和AHK5)序列相似的磷酸感应激酶基因HK5和HK3在干旱胁迫下表达上调, 与拟南芥中不依赖细胞分裂素的AHK5序列接近的HK6则表达下调, 进一步验证上述推测; 干旱胁迫下抗旱能力不同的水稻株系其TCS基因表达谱没有明显差异, 推测TCS基因差异表达可能源于对干旱胁迫反应, 而其表达对抗旱能力的增强还有待进一步研究。