Gibberellin delays kiwifruit postharvest ripening via the <i>AcDELLA</i> gene family

Gibberellin (GA) has a significant regulatory role in the growth and development of higher plants. DELLA proteins are the key negative regulators of the gibberellin signalling pathway. However, the genomic overview of the kiwifruit <i>DELLA</i> gene family and their function on kiwifruit ripening has not yet been studied. Exogenous GA₃ can effectively maintain postharvest kiwifruit firmness and delay the ripening process. Eight <i>AcDELLA</i>s genes were identified from the kiwifruit genome and named as <i>AcDELLA1</i> to <i>AcDELLA8</i> by the order of chromosomal localization. Sequence analysis confirmed that the N terminus of all eight AcDELLA proteins contained high-conservation DELLA and TVHYNP motifs. Phylogenetic analysis showed that <i>AcDELLA1</i>, and <i>AcDELLA3</i> were highly homologous with <i>AcDELLA5</i> and <i>AcDELLA6.</i> The gene expression of <i>AcDELLA3</i>/<i>4</i>/<i>5</i>/<i>6</i> were significantly induced by GA₃ treatment, while, GA₃ delayed the expression of <i>AcDELLA7</i>, and <i>AcDELLA8</i> maintained higher level in GA₃ group than in control. Correlation analysis between physiological parameters and <i>AcDELLA</i>s gene expression demonstrated that <i>AcDELLA3</i>/<i>4</i>/<i>5</i>/<i>7</i>/<i>8</i> had a marked correlation with firmness, TSS, and ethylene production. All these results showed that GA₃ treatment could inhibit kiwifruit postharvest ripening and prolong storage time, and these GA-responsive <i>DELLA</i>s may play important roles in this process.