Two ATP Binding Cassette G (ABCG) Transporters, OsABCG26 and OsABCG15, Collaboratively Regulate Rice Male Reproduction

Abstract

Male reproduction in higher plants requires the support of various metabolites, including lipid molecules produced in the innermost anther wall layer (the tapetum), but how the molecules are allocated among different anther tissues remains largely unknown. Previously, rice (Oryza sativa) ATP binding cassette G15 (ABCG15) and its Arabidopsis (Arabidopsis thaliana) ortholog were shown to be required for pollen exine formation. Here, we report the significant role of OsABCG26 in regulating the development of anther cuticle and pollen exine together with OsABCG15 in rice. Cytological and chemical analyses indicate that osabcg26 shows reduced transport of lipidic molecules from tapetal cells for anther cuticle development. Supportively, the localization of OsABCG26 is on the plasma membrane of the anther wall layers. By contrast, OsABCG15 is polarly localized in tapetal plasma membrane facing anther locules. osabcg26 osabcg15 double mutant displays an almost complete absence of anther cuticle and pollen exine, similar to that of osabcg15 single mutant. Taken together, we propose that OsABCG26 and OsABCG15 collaboratively regulate rice male reproduction: OsABCG26 is mainly responsible for the transport of lipidic molecules from tapetal cells to anther wall layers, whereas OsABCG15 mainly is responsible for the export of lipidic molecules from the tapetal cells to anther locules for pollen exine development.

A Rice Ca2+ Binding Protein Is Required for Tapetum Function and Pollen Formation

“…the epidermis, endothecium, and tapetum. In Figure 9, the anther images show the morphology of tapetal cells, which is consistent with a previous report (Zhao et al, 2015). PM-YC3.6, which is a plasma membrane targeted version of YC3.6, is able to distinguish the faint Ca 2+ signal at the cytosolic side of the plasma membrane from the strong autofluorescence of anthers.…”

“…Several lipid metabolism-related genes, such as Defective Pollen Wall (DPW), CYP704B2, and CYP703A3 have been reported to be essential for rice exine formation (Shi et al, 2011;Li et al, 2010;Yang et al, 2014b;Shi et al, 2015;. Additionally, sporopollenin precursor transport-related genes, such as Postmeiotic Deficient Anther1 (OsABCG15/PDA1), OsABCG26, and OsC6 Qin et al, 2013;Zhu et al, 2013;Zhao et al, 2015), are also required for pollen exine formation (Supplemental Fig. S1).…”

Construction of a male sterility system for hybrid rice breeding and seed production using a nuclear male sterility gene

“…In rice, the lipid precursors for anther surface cuticle and sporopollenin are presumably produced in the tapetum, and then secreted via Ubisch bodies and transported to the anther and microspore surfaces (9,17). Several rice male sterile mutants with defects in tapetum lipid metabolism or transportation also have defects in the development of Ubisch bodies, pollen exine, and anther surface cuticle (20)(21)(22). Moreover, the expression of several genes regulating tapetum PCD and synthesis/transportation of sporopollenin precursors displayed abnormal expression patterns in osnp1-1 (Fig.…”

Defective Pollen Wall 2 (DPW2) Encodes an Acyl Transferase Required for Rice Pollen Development

“…11). The produced aromatic acids and v-hydroxylated aliphatic acids are often cross linked to form phenolics for the biosynthesis of precursors of anther cutin and pollen exine (Wehling et al, 1989;Gubatz et al, 1993;Negri et al, 2011;Yang et al, 2014;Zhao et al, 2015;Zhang and Liang, 2016) and for pollen coat (Grienenberger et al, 2009). In this study, we provide morphological, chemical, histochemical, and in vitro enzyme activity data to suggest that DPW2 is mainly responsible for the polymerization of lipidic and phenolic pollen wall precursors.…”

“…Phenolics such as ferulate and p-coumarate ester are also constituents of the anther Zhao et al, 2015) and pollen walls (Wehling et al, 1989;Gubatz et al, 1993;Grienenberger et al, 2009;Negri et al, 2011). In suberized cell walls, the aromatic phenolics, mainly p-coumaric and ferulic acid, link the aliphatic domain to cell wall polysaccharides (Bernards, 2002).…”