JAZ1 attenuates drought resistance by regulating JA and ABA signaling in rice. JAZ1 attenuates drought resistance by regulating JA and ABA signaling in rice

Jasmonates (JA) and abscisic acid (ABA) are phytohormones known to play important roles in plant response and adaptation to various abiotic stresses including salinity, drought, wounding, and cold. JAZ (JASMONATE ZIM-domain) proteins have been reported to play negative roles in JA signaling. However, direct evidence is still lacking that JAZ proteins regulate drought resistance. In this study, OsJAZ1 was investigated for its role in drought resistance in rice. Expression of OsJAZ1 was strongly responsive to JA treatment, and it was slightly responsive to ABA, salicylic acid, and abiotic stresses including drought, salinity, and cold. The OsJAZ1-overexpression rice plants were more sensitive to drought stress treatment than the wild-type rice Zhonghua 11 (ZH11) at both the seedling and reproductive stages, while the jaz1 T-DNA insertion mutant plants showed increased drought tolerance compared to the wild-type plants. The OsJAZ1-overexpression plants were hyposensitive to MeJA and ABA, whereas the jaz1 mutant plants were hypersensitive to MeJA and ABA. In addition, there were significant differences in shoot and root length between the OsJAZ1 transgenic and wild-type plants under the MeJA and ABA treatments. A subcellular localization assay indicated that OsJAZ1 was localized in both the nucleus and cytoplasm. Transcriptome profiling analysis by RNA-seq revealed that the expression levels of many genes in the ABA and JA signaling pathways exhibited significant differences between the OsJAZ1-overexpression plants and wild-type ZH11 under drought stress treatment. Quantitative real-time PCR confirmed the expression profiles of some of the differentially expressed genes, including OsNCED4, OsLEA3, RAB21, OsbHLH006, OsbHLH148, OsDREB1A, OsDREB1B, SNAC1, and OsCCD1. These results together suggest that OsJAZ1 plays a role in regulating the drought resistance of rice partially via the ABA and JA pathways. Overall design: Transcriptome analysis of ZH11, OsJAZ1-OE plants under both severe drought stress and normal growth conditions.

茉莉素（Jasmonates, JA）与脱落酸（abscisic acid, ABA）是两类关键植物激素，在植物响应并适应盐胁迫、干旱、机械损伤与低温等多种非生物胁迫的过程中发挥重要调控功能。JAZ蛋白（JASMONATE ZIM-domain, JAZ）已被报道可在JA信号通路中充当负调控因子，但目前仍缺乏JAZ蛋白调控水稻抗旱性的直接实验证据。
本研究以水稻OsJAZ1基因为研究对象，探究其在水稻抗旱性调控中的作用。实验结果显示，OsJAZ1的表达对JA处理具有显著响应，同时对ABA、水杨酸以及干旱、盐胁迫、低温等非生物胁迫仅表现出微弱应答。
与野生型中花11（Zhonghua 11, ZH11）相比，过表达OsJAZ1的转基因水稻在苗期与生殖期均对干旱胁迫更为敏感；而T-DNA插入突变体jaz1的抗旱性则显著高于野生型植株。此外，OsJAZ1过表达植株对茉莉酸甲酯（MeJA）与ABA的敏感性降低，而jaz1突变体则对二者表现出超敏感表型。在MeJA与ABA处理条件下，OsJAZ1转基因植株与野生型植株的地上部长度及根长均存在显著差异。
亚细胞定位实验表明，OsJAZ1蛋白同时定位于细胞核与细胞质中。通过RNA测序（RNA-seq）开展的转录组分析显示，在干旱胁迫处理下，OsJAZ1过表达植株与野生型中花11（ZH11）体内诸多参与ABA与JA信号通路的基因表达量存在显著差异。实时定量聚合酶链式反应（Quantitative real-time PCR）验证了部分差异表达基因的表达模式，包括OsNCED4、OsLEA3、RAB21、OsbHLH006、OsbHLH148、OsDREB1A、OsDREB1B、SNAC1及OsCCD1。
上述研究结果共同表明，OsJAZ1可部分通过ABA与JA信号通路参与调控水稻的抗旱性。
整体实验设计：对野生型中花11（ZH11）与OsJAZ1过表达植株分别在严重干旱胁迫及正常生长条件下开展转录组分析。