Arabidopsis Di19 functions as a transcription factor and modulates PR1, PR2, and PR5 expression in response to drought stress.

The Arabidopsis Di19 (Drought-induced) gene family encodes seven Cys2/His2-type zinc-finger proteins, most with unknown functions. Here, we report that Di19 functioned as a transcriptional regulator and was involved in Arabidopsis responses to drought stress through up-regulation of pathogenesis-related PR1, PR2, and PR5 gene expressions. The Di19 T-DNA insertion mutant di19 was much more sensitive to drought stress, whereas the Di19-overexpressing lines were much more tolerant to drought stress compared with wild-type plants. Di19 exhibited transactivation activity in our yeast assay, and its transactivation activity was further confirmed in vivo. DNA-binding analysis revealed that Di19 could bind to the TACA(A/G)T element and chromatin immunoprecipitation (ChIP) assays demonstrated that Di19 could bind to the TACA(A/G)T element within the PR1, PR2, and PR5 promoters. qRT-PCR results showed that Di19 promoted the expressions of PR1, PR2, and PR5, and these heightened expressions were enhanced by CPK11, which interacted with Di19 in the nucleus. Similarly to the Di19-overexpressing line, PR1-, PR2-, and PR5-overexpressing lines also showed the drought-tolerant phenotype. The pre-treatment with salicylic acid analogs INA can enhance plants' drought tolerance. Taken together, these data demonstrate that Di19, a new type of transcription factor, directly up-regulates the expressions of PR1, PR2, and PR5 in response to drought stress, and its transactivation activity is enhanced by CPK11.

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