Genome-wide identification of the NAC gene family in taro and functional analysis of CeNAC48 in starch biosynthesis.

Abstract

Taro (Colocasia esculenta (L.) Schott) is an important perennial corm crop, and its corm expansion is accompanied by starch synthesis and accumulation. NAC transcription factors (TFs) serve as important regulators of plant growth and stress adaptation. However, their regulatory mechanisms underlying corm development and starch biosynthesis in taro remain largely unknown. In this study, a total of 83 NAC genes (CeNACs) were identified in taro. The evolution of the CeNAC gene family was mainly driven by segmental duplication events followed by purifying selection. Promoter cis-element analysis indicated that most CeNAC genes respond to light and methyl jasmonate (MeJA) signals. Transcriptomic and qRT-PCR analyses revealed that the expression of CeNAC48 was negatively correlated with the starch accumulation in taro. CeNAC48 was localized in the nucleus, endoplasmic reticulum and plasma membrane, and had transcriptional activation activity. Stable overexpression of CeNAC48 in tobacco significantly decreased starch content; consistently, overexpression of CeNAC48 in taro calli also reduced starch content, whereas silencing of CeNAC48 resulted in starch accumulation. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA) and dual-luciferase reporter (LUC) assays confirmed that CeNAC48 directly binds to the promoters of CeAGPS1 and CeBAM. By repressing CeAGPS1 and activating CeBAM, CeNAC48 negatively regulates starch synthesis in taro. These findings identify CeNAC48 as a key conserved regulator of starch biosynthesis with cross-species application potential.This study reports the first genome-wide identification of the NAC gene family in taro, and provides a valuable molecular target for genetic improvement of taro quality.