Autophagy modulates male fertility in Arabidopsis

Macroautophagy/autophagy is a highly conserved catabolic process in eukaryotes and plays pivotal roles in regulating male fertility and sexual reproduction. In metazoans, mutations in core ATG (autophagy related) proteins frequently result in severe defects in sperm formation and maturation, resulting in male sterility. In contrast, autophagy has traditionally been considered dispensable for reproduction in Arabidopsis thaliana, as most atg mutants can complete fertilization and produce viable progeny without apparent reproductive defects. We recently systematically re-assessed the role of autophagy in Arabidopsis male gametophyte development and fertility using atg5 and atg7 mutants, and the double mutant. These mutants exhibited partial defects in pollen germination, pollen tube growth and seed production compared to the wild type (WT). Furthermore, our findings reveal that autophagy is essential for modulating actin dynamic organization during sperm cell formation within pollen grains and for supporting pollen tube elongation. This is achieved through the selective degradation of actin depolymerizing factors ADF7 and PFN2/Profilin2. NBR1 is identified as a key receptor mediating this process. This study provides valuable insights into the evolutionary conservation and functional divergence of autophagy in modulating male fertility, highlighting distinctions between plant and mammalian systems.