Abscisic acid (ABA) is a very important hormone in plants. However, the mechanisms of ABA response to abiotic stresses in rice are still relatively unknown. In the ABA biosynthetic pathway, 9-cis-epoxycarotenoid dioxygenase (NCED) is the key enzyme. To study the function of OsNCED3 in abiotic stress tolerance in rice, the team of Yuan Huang from Hunan Normal University in China used the CRIPR-Cas9 system.
The OsNCED3 gene was found to be expressed in various tissues under normal condition. Its expression was highly induced by NaCl, PEG, and H2O2 stress, suggesting the roles for OsNCED3 in several abiotic stress tolerances in rice. To further specify the role of OsNCED3, the team generated nced3 mutants using CRISPR and compared them to wildtypes.
The mutants exhibited earlier seed germination, increased sensitivity to water stress and H2O2 stress and increased stomata aperture under water stress and delayed leaf senescence. Further analysis found that nced3 mutants contained lower ABA content compared with wildtype plants. Meanwhile, overexpression of OsNCED3 in transgenic plants enhanced water stress tolerance, promoted leaf senescence and increased ABA content.
Results suggest that OsNCED3 controls seed dormancy, plant growth, abiotic stress tolerance, and leaf senescence by regulating ABA synthesis in rice.

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