Alterations in arabinogalactan proteins in banana peel during fruit development and ripening.

Background and aims: Arabinogalactan proteins (AGPs) are vital for supporting the structural aspects of plant growth and development. However, knowledge regarding their role in the growth and ripening of banana fruit remains elusive.

Methods: In the present study, changes in the spatiotemporal distribution, transcriptional level of different AGPs and their content during the development and ripening of banana fruit were investigated.

Key results: Immunofluorescence labelling results indicated that banana AGP components were predominantly present in the epidermis, xylem and phloem. RNA-sequencing analysis revealed that during fruit development, the expression of 88 out of 259 MaAGP genes decreased, while 29 displayed opposite expression. Nevertheless, some genes demonstrated peak expression at stage II, aligning closely with the levels of AGP epitopes identified by JIM4, JIM8, LM2 and JIM13 antibodies. Ethylene treatment raised the expression of 31 members and inhibited 57 of them. This is supported by a decreasing trend in the AGP epitope level of LM2, MAC204 and MaFLA27 antibodies, whereas it was inverse for JIM8 antibody. Consequently, AGP content showed a decline in expression during the development and ripening processes. The profusion of plant hormone and growth-responsive cis-acting regulatory elements found in the 2-kb upstream region of MaAGPs further indicates the involvement of AGPs in developmental and ripening activities. MaSAUR39, MaSYD1/2, MaF-box1/2/3, MaBP1, MaRIMA1, MaLLR1, MaATMRP1, MaBBR1/2 and MaPPS1 were among the proteins that interacted the most and are essential for plant growth and development.

Conclusions: The findings of this study offer new understanding into the role of AGPs in banana fruit growth and ripening.