Disruption of BG14 results in enhanced callose deposition in developing seed and decreases seed longevity and seed dormancy in Arabidopsis.

Seed longevity is an important trait for agriculture and genetic resource conservation. β-1,3-glucanases were first recognized as pathogenesis-related proteins involved in plant defense, but their roles in seeds are largely unknown. Here, we report a glycosylphosphatidylinositol-anchored β-1,3-glucanase, BG14, that degrades callose in seed embryos and functions in seed longevity and dormancy in Arabidopsis. Loss-of-function of BG14 significantly decreased seed longevity, while functional reversion (RE) and overexpression (OE) lines reversed and increased the impaired phenotype, respectively. Loss-of-function of BG14 enhanced callose deposition in the embryos of mature seeds, which was confirmed by quantitative determination and the decreased callose degrading ability in bg14. The drop-ANd-See assay revealed that the fluorescence signal in bg14 was significantly lower than those of the other three genotypes. BG14 is located in the periphery of the cell wall and can completely merge with callose at the plasmodesmata of epidermal cells. BG14 was highly expressed in developing seeds and was induced by aging and abscisic acid (ABA). Loss-of-function of BG14 showed a variety of phenotypes related to ABA, including reduced seed dormancy and reduced responses to ABA and pacolblltrazol treatments, while OE lines showed the opposite phenotype. The reduced ABA response is because of decreased ABA level and lowered expression of ABA synthesis genes in bg14. Taken together, this study demonstrated that BG14 is a bona fide BG, that mediates callose degradation in the plasmodesmata of embryo cells, transcriptionally regulates ABA synthesis genes in developing seeds, and positively affects seed longevity and dormancy in Arabidopsis.