Transgenic overexpression of UIP1, an interactor of the 3′ untranslated region of the Rubisco small subunit mRNA, increases rice tolerance to drought
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Gene regulation at the post-transcriptional level is a well-organized process to adjust plants in response to environmental changes. Here, we identified a novel RNA-binding protein (RBP) possessing a CBS (cystathionine-β-synthase) domain through yeast three-hybrid screening. This RBP, 3′-UTR-interacting protein 1 (UIP1), interacts with 3′ untranslated region of the Rubisco small subunit mRNA (3′ RbcS)—the major mRNA element that mediates the stress-induced mRNA decay (SMD) under drought and salt stress conditions. Six deletion constructs were made to delineate the binding domain of the UIP1 protein. Co-transformation of yeast with these constructs together with three different hybrid RNAs in various combinations showed that deletion of 51 N-terminal amino acids resulted in a loss of sequence-specific binding affinity. Further deletion at the region between 52 and 212 amino acids revealed that the CBS domain of UIP1 is necessary for binding to 3′ RbcS. Transgenic overexpression of UIP1 in rice resulted in an increase in tolerance to drought stress at the vegetative stage of growth. Under drought, high salt and low temperature conditions, the maximum photochemical efficiency of photosystem II (Fv/Fm) of UIP1 plants was higher than those of the nontransgenic plants. Interestingly, the effect of UIP1 overexpression on tolerance to stress was much more pronounced under drought than under high salt and low temperature conditions. Taken together, our results demonstrate that UIP1 interacts with 3′ untranslated region of RbcS1 mRNA and increases tolerance of transgenic overexpressors to drought stress.