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Abstract

Starch branching enzyme (SBE), which is one of the key enzymes associated with amylopectin biosynthesis, plays important roles in variable biological processes. Despite its importance, SBE is rarely studied in the banana (Musa acuminata L.) which is a typical starchy fruit. Here, a family of ten SBE proteins (MaSBE) was firstly identified through genome-wide characterization in M. acuminata, which could be clustered into three subfamilies. Systematic transcriptome analysis revealed temporal and spatial expression variations of MaSBE genes and differential response patterns under abiotic and biotic stresses in both banana genotypes, Fen Jiao (FJ) and BaXi Jiao (BX). Moreover, MaSBE2.4 was temporally regulated during fruit development and ripening as well as in response to various abiotic/biotic stresses in both genotypes. Specifically, MaSBE2.3 expression level was higher in FJ than in BX following cold, salt, and drought stress treatments, and it was specifically induced by fungal infection in BX. Characterization of hormone-and stressrelated cis-acting elements in the promoters of MaSBE genes suggests their multiple biological functions. In conclusion, our study provides new insights into the complex transcriptional characteristics of the SBE genes, and demonstrates their crucial roles in improving amylopectin biosynthesis and strengthening stress resistance in banana.