Although the functions of WRKY transcription factors in drought resistance are well known, their regulatory mechanisms in response to drought by stabilising photosynthesis remain unclear. Here, a differentially expressed PoWRKY71 gene that was highly expressed in drought-treated Paeonia ostii leaves was identified through transcriptome analysis. PoWRKY71 positively responded to drought stress with significantly enhanced expression patterns and overexpressing PoWRKY71 in tobacco greatly improved plant tolerance to drought stress, whereas silencing PoWRKY71 in P. ostii resulted in a drought-intolerant phenotype. Furthermore, lower chlorophyll contents, photosynthesis, and inhibited expression of photosynthesis-related light-harvesting chlorophyll a/b-binding 151 (CAB151) gene were found in PoWRKY71-silenced P. ostii. Meanwhile, a homologous system indicated that drought treatment increased PoCAB151 promoter activity. Interactive assays revealed that PoWRKY71 directly bound on the W-box element of PoCAB151 promoter and activated its transcription. In addition, PoCAB151 overexpressing plants demonstrated increased drought tolerance, together with significantly higher chlorophyll contents and photosynthesis, whereas these indices were dramatically lower in PoCAB151-silenced P. ostii. The above results indicated that PoWRKY71 activated the expression of PoCAB151, thus stabilising photosynthesis via regulating chloroplast homeostasis and chlorophyll content in P. ostii under drought stress. This study reveals a novel drought-resistance mechanism in plants and provides a feasible strategy for improving plant drought resistance via stabilising photosynthesis.

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