High temperature elevates carotenoid accumulation of banana fruit via upregulation of MaEIL9 module

Banana is a good source of carotenoids, which are bioactive metabolites with health beneficial properties for human. However, the molecular mechanism of carotenoid accumulation in banana fruit is largely unclear. In this study, we found that high temperature elevated carotenoid production in banana pulp, which is presumably due to upregulation of a subset of carotenogenic genes as well as a carotenoid biosynthesis regulator MaSPL16. Moreover, an ethylene signaling component MaEIL9 was identified, whose transcript and protein contents were also induced by high temperature. In addition, MaEIL9 positively regulates transcription of MaDXR1, MaPDS1, MaZDS1 and MaSPL16 through directly targeting their promoters. Overexpression of MaEIL9 in tomato fruit substantially increased the expression of carotenoid formation genes and elevated carotenoid content. Importantly, transiently silencing MaEIL9 in banana fruit weakened carotenoid production caused by high temperature. Taken together, these results indicate that high temperature induces carotenoid production in banana fruit, at least in part, through MaEIL9-mediated activation of MaDXR1, MaPDS1, MaZDS1 and MaSPL16 expression.

Automated summary

Banana is a good source of carotenoids, and in this study, it was found that high temperature increases carotenoid production in banana fruit. This increase is likely due to the upregulation of specific carotenogenic genes and the carotenoid biosynthesis regulator MaSPL16. Moreover, the ethylene signaling component MaEIL9 was identified as being induced by high temperature, and it positively regulates the transcription of carotenoid formation genes. Overexpression of MaEIL9 in tomato fruit also increased carotenoid content. Transient silencing of MaEIL9 in banana fruit weakened carotenoid production caused by high temperature. Overall, these findings suggest that high temperature induces carotenoid production in banana fruit through the activation of specific genes mediated by MaEIL9.