Overexpression of 9-<em>cis</em>-Epoxycarotenoid Dioxygenase Gene, <em>IbNCED1</em>, Negatively Regulates Plant Height in Transgenic Sweet Potato

Abstract

Plant height is one of the key agronomic traits for improving the yield of sweetpotato. The phytohormones, especially gibberellins (GAs) are crucial to regulate plant height. The 9-cis-epoxycarotenoid dioxygenase (NCED) is the key enzyme for abscisic acid (ABA) biosynthesis signalling in higher plants. However, its role in regulating plant height has not been reported to date. Here, we cloned a NCED gene, IbNCED1, from sweetpotato cultivar Jishu26. This gene encoded the 587-amino acid polypeptide containing an NCED superfamily domain. The expression level of IbNCED1 was highest in the old tissues in the field-grown Jishu26. The expression of IbNCED1 was induced by ABA and GA. Overexpression of IbNCED1 promoted the accumulation of ABA and inhibited the content of active GA3 and plant height, and affected the expression levels of genes involved in the GA metabolic pathway. IbNCED1 overexpression reduced sensitivity to GA3 and exogenous application of GA3 could rescue the dwarf phenotype. In conclusion, we suggest that IbNCED1 regulates plant height and development by controlling the accumulation of active GA3 signalling pathway in transgenic sweetpotato.