β-1,3-GLUCANASE10 regulates tomato development and disease resistance by modulating callose deposition.

Abstract

β-1,3-Glucanases are considered key regulators responsible for the degradation of callose in plants, yet little is known about the role and mode of action of their encoding genes in tomato (Solanum lycopersicum). In the present study, we identified the β-1,3-glucanase encoding gene β-1,3-GLUCANASE10 (SlBG10) and revealed its regulation in tomato pollen and fruit development, seed production, and disease resistance by modulating callose deposition. Compared to wild-type or SlBG10 overexpressing (SlBG10-OE) lines, knockout of SlBG10 caused pollen arrest and failure to set fruit with reduced male rather than female fecundity. Further analyses showed that SlBG10-knockout promoted callose deposition in anther at the tetrad-to-microspore stages, resulting in pollen abortion and male sterility. Moreover, loss-of-function SlBG10 delayed degradation of endosperm cell wall calloses during cellularization and impeded early seed development. We also uncovered that Botrytis cinerea infection induces SlBG10 expression in wild-type tomato, and the knockout lines showed increased callose accumulation in fruit pericarps, reduced susceptibility to B. cinerea and enhanced antioxidant capacity to maintain tomato fruit quality. However, expression of genes encoding cell wall hydrolases decreased in SlBG10-knockout tomatoes and thus led to an increase in pericarp epidermal thickness, enhancement in fruit firmness, reduction of fruit water loss and extension of tomato shelf life. These findings not only expand our understanding of the involvement of β-1,3-glucanases as callose regulators in multiple developmental processes and pathogen resistance, but also provide additional insight into the manipulation of multi-agronomic traits for targeted tomato breeding.