水稻 OsRR6 與 OsRR11 參與鹽分逆境根系發育之功能研究

Abstract

為因應氣候變遷以確保糧食安全，了解作物於非生物逆境下之反應機制與其理想株型為重要的農業課題。植物荷爾蒙調控作物生長發育並參與非生物逆境反應，其中細胞分裂素訊息傳遞所扮演之角色亦為目前探討對象。實驗室先前研究利用 CRISPR/Cas9 基因編輯技術建立水稻細胞分裂素訊息傳導系統下游 Type-A RRs 中 osrr6/osrr11 雙重突變株，於鹽害逆境下顯示 OsRR6 及 OsRR11 為耐鹽性之正向調控因子。在全基因體轉錄分析指出 OsRR6 與 OsRR11 可能參與鹽害逆境下離層酸之反應調控。為釐清鹽害逆境下 OsRR6 及 OsRR11個別功能性與其是否參與 ABA 調控之反應路徑，本試驗首先分離出 osrr6 與 osrr11 單突變株，發現 OsRR11 相較於 OsRR6 為調控鹽害耐受性之主要角色，基因表現分析顯示 OsRR6 與 OsRR11 同時參與鹽害逆境下鈉離子運移、細胞分裂素含量變化，離層酸依賴性與非依賴性路徑。而由單突變株結果顯示相較於 OsRR11，OsRR6 於鹽害逆境下 ABA 影響之生理作用中扮演正向調控之功能。此外，鹽害逆境回復後，osrr6/11 突變株具有較野生型少之不定根，且因鹽害逆境下細胞分裂素代謝及離層酸訊息相關基因具差異表現，推測 OsRR6 和 OsRR11 可能經由其他荷爾蒙之交互作用調控根系生長發育，透過外施細胞分裂素氧化酵素抑制劑與離層酸，可見 osrr6/11 突變株相較於野生型形成較少之側根數目及較低之側根密度，初步顯示 OsRR6 與 OsRR11 負向調控對於離層酸與內源性細胞分裂素抑制根系發育之敏感性。綜合上述結果，本試驗確立水稻 OsRR6 與 OsRR11 參與鹽分逆境根系發育之生理功能。

To cope with the climate change, understanding the mechanism of crops under abiotic stress and its ideotype is an important agriculture issue. Plant hormones are known to regulate plant growth and abiotic stress responses, and the role of cytokinin signaling in abiotic stress response currently is still under investigation. Previous studies in our lab using CRISPR/Cas9 to generate double cytokinin signaling type-A response regulator (osrr6/osrr11) mutants had shown that OsRR6 and OsRR11 play a positive role in response to salinity stress, and the transcriptomic analysis further suggest that they may be involved in the cross-talk between ABA under salinity stress response. To evaluate whether OsRR6 and/or OsRR11 interact with ABA signaling in the present or absence salinity stress, this study first reveals OsRR11 plays a more important role than OsRR6 under salinity stress. Both of them participate in the regulation of sodium transport, cytokinin metabolism, ABA-dependent and independent pathway associated gene. In comparing with OsRR11, OsRR6 positively regulates the ABA responses under salinity stress. Besides, osrr6/11 mutants developed few adventitious root than wild type after the recovery of the salinity stress. Considering there are cytokinin and ABA associated differential expression genes under salinity stress, I suggest that OsRR6 and OsRR11 interact with other plant hormones in root developmental system. Under exogenous application of ABA and inhibitor of cytokinin oxidase/dehydrogenase, osrr6/11 mutants have reduced lateral root number and lower lateral root density than wild type. The results show that OsRR6 and OsRR11 may positively regulate root growth and development by inhibition sensitivity of cytokinin and ABA. Collectively, this study emphasizes the function of rice response regulator OsRR6 and OsRR11 in mediating various responses in root development under different treatments.