水稻細胞分裂素反應調節蛋白OsRR9、OsRR10與離層酸反應之交互作用

Abstract

細胞分裂素 (cytokinin) 屬於一種植物激素，參與調控植物的許多生理功能，近年陸續有研究指出細胞分裂素的訊息傳遞會影響植物在逆境下的反應。OsRR9以及OsRR10是細胞分裂素下游的A型反應調節蛋白 (type-A RR)，可接收磷酸根並負向調控細胞分裂素的訊息傳遞。本實驗室先前研究中osrr9/10突變株轉錄體研究中發現許多離層酸生合成以及下游轉錄因子的基因表現相較於野生型受到抑制，對植株外施離層酸處理後觀察osrr9/10雙重突變株與野生型相比氣孔導度與水分蒸散速率抑制情形較輕微，並在處理4天後保有較高的地上部鮮重和乾重，而在種子萌芽時期進行離層酸處理後突變株在2天後有相對較低的發芽抑制情形；對植株進行離層酸前處理後野生型與突變株相比相對水分含量亦有顯著提升，指出osrr9/10突變可能會抑制植物體中離層酸的訊號，進而降低其對於離層酸的敏感度，並且可能會影響植株在乾旱、滲透逆境下的耐受性。本文結果顯示OsRR9與OsRR10可能與離層酸反應之間具有交互作用，並在離層酸參與調節氣孔和植物生長的訊息中扮演正向調節的角色。

cytokinin is a group of plant hormone well known for its role in numerous aspects of growth and development in plants, such as regulating cell division and differentiation, organ morphogenesis, apical dominance and chlorophyll degradation. Recently, it is reported that cytokinin might also participates in stress response in plants as well. OsRR9 and OsRR10 are two type-A response regulators (type-A RR) downstream of cytokinin, which could receive phosphate and inhibit cytokinin signal response via negative feedback. Previous study has showed that the gene expression of ABA biosynthesis and its downstream transcriptional factors were inhibited in osrr9/10 mutant line. After treated with ABA, plant growth, stomatal conductance, evapotranspiration rate, and germination rate were less suppressed in osrr9/10 mutant compared with wild type. In addition, pretreating ABA increased relative water content in wild type under osmotic stress but not in osrr9/10 mutant, suggesting that ABA sensitivity decreased in mutant and might affect plant stress tolerance. These results showed that OsRR9 and OsRR10 might interact with ABA signaling and play a positive role in ABA response.