Abstract
Jasmonates (JAs) and abscisic acid (ABA) are phytohormones known 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 (WT) 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 WT 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 WT 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 WT 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.
Highlights
Due to their sessile nature, plants have to face variable environmental stresses including drought, high salinity, cold, and heat during their growth and development
The results showed that OsJAZ1 was strongly induced by MeJA (Figure 1A), suggesting that JAZ1 may be involved in JA signaling
Considering the biochemical function of JASMONATE ZIM-domain (JAZ) proteins, these results suggest that OsJAZ1 may participate in the regulation of the responses to abiotic stresses and multiple phytohormones
Summary
Due to their sessile nature, plants have to face variable environmental stresses including drought, high salinity, cold, and heat during their growth and development. Plants respond and adapt to the adverse cues throughout their life cycle by coordinating an array of biochemical and physiological changes. Phytohormones, such as abscisic acid (ABA) and jasmonates (fatty acid-derived oxylipins, JAs), play important roles in promoting plant defense against abiotic stresses (Verma et al, 2016). Under normal or JA-absent conditions, JAZ proteins bind to transcription factors (TFs) and inhibit their activities by recruiting the TOPLESS (TPL) co-repressor or by directly recruiting histone-modifying proteins such as HDA6. These TFs can bind to the G-box of JA- and JA-Ile-responsive genes. Under any stress conditions or developmental processes in which the levels of endogenous JA-Ile (bioactive jasmonylisoleucine) are increased, the binding of JA-Ile to the COI1-JAZ co-receptor will lead to the degradation of JAZs via the 26S proteasome, and the JA signaling responses and downstream genes are activated
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