Abstract
Sugars Will Eventually be Exported Transporters (SWEET) are a novel type of sugar transporter that plays crucial roles in multiple biological processes. From banana, for the first time, 25 SWEET genes which could be classified into four subfamilies were identified. Majority of MaSWEETs in each subfamily shared similar gene structures and conserved motifs. Comprehensive transcriptomic analysis of two banana genotypes revealed differential expression patterns of MaSWEETs in different tissues, at various stages of fruit development and ripening, and in response to abiotic and biotic stresses. More than 80% MaSWEETs were highly expressed in BaXi Jiao (BX, Musa acuminata AAA group, cv. Cavendish), in sharp contrast to Fen Jiao (FJ, M. acuminata AAB group) when pseudostem was first emerged. However, MaSWEETs in FJ showed elevated expression under cold, drought, salt, and fungal disease stresses, but not in BX. Interaction networks and co-expression assays further revealed that MaSWEET-mediated networks participate in fruit development signaling and abiotic/biotic stresses, which was strongly activated during early stage of fruit development in BX. This study provides new insights into the complex transcriptional regulation of SWEETs, as well as numerous candidate genes that promote early sugar transport to improve fruit quality and enhance stress resistance in banana.
Highlights
In plants, sugars provide energy, essential signal molecule components, and metabolic intermediates for plant growth and development, and play crucial roles in both abiotic and biotic stress responses[1,2,3,4,5]
At 2 d post-infection (DPI) since infection, 3 gene pairs showed uniform up-regulation in BaXi Jiao (BX), 18 gene pairs were down-regulation (Fig. 11C and Supplementary Table S12); in Fen Jiao (FJ), 4 gene pairs showed uniform up-regulation, while 15 pairs showed uniform down-regulation (Fig. 11D and Supplementary Table S12). These results show the potential functional roles of MaSWEET genes in defense against fungal diseases in banana, with more gene pairs found uniformly down-regulated in BX and FJ at 2 DPI since infection
Using the genome wide identification approach, we have identified 25 MaSWEET genes in M. acuminata, and made a comparative analysis in two genotypes including BX and FJ
Summary
Sugars provide energy, essential signal molecule components (carbon), and metabolic intermediates for plant growth and development, and play crucial roles in both abiotic and biotic stress responses[1,2,3,4,5]. In V. vinifera, VvSWEET4 expression was reported to participate in the interaction with Botrytis cinerea[4] Taken together, these studies have revealed many important roles of the SWEET gene family in the regulation of plant growth, development, and responses to abiotic and biotic stresses. Despite of its importance in fruit quality, plant growth and stress regulation, SWEET genes have not been studied in banana. We characterized interaction networks and co-expression patterns of MaSWEETs in early stages of fruit development and under abiotic and biotic stresses. This comprehensive study serve to facilitate our understanding of MaSWEET associated fruit development processes and stress responses, and provide a foundation for future studies of crop improvement involving SWEETs
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