Abstract
Autophagy is one of the cellular processes that break down cellular components during senescence, starvation, and stress. The susceptibility of plant pollen development to high-temperature (HT) stress is well known, but the involvement of autophagy in HT injury is yet to be clarified. Here, we found that following transfer to 30 °C, all autophagy-deficient (atg) mutants (atg2-1, 5-1, 7-2, and 10-1) of Arabidopsis thaliana tested displayed visibly impaired pollen development and anther dehiscence. HT-induced male sterility significantly increased in the atg mutants, but the degree of HT-induced obstacles did not change between the wild type (WT) and mutants from the seedling stage to the bolting stage. Cytological analyses showed that 30 °C promoted autophagy and autolysosome formation in both anther wall cells and microspores in developing anthers of WT, but the atg5-1 mutant did not show completion of tapetum degeneration and microspore maturation. HT upregulated hydrogen peroxide and dehydroascorbate reductase 1 production in both WT and atg5-1 anthers, but the basal levels were already higher in the mutant. HT repressed expression of UNDEAD and its regulator MYB80, which are required for tapetal programmed cell death (PCD) for proper pollen development. Taken together, our results suggest that autophagy functions in tapetum degeneration and pollen development during HT-caused tapetal PCD abortion.
Highlights
Arabidopsis atg mutants are hypersensitive to High15 temperature (HT) injury and show sporophytic male sterility
Plant autophagy is involved in senescence, and in responses to stress due to nutrient starvation, pathogens, drought, salt, and oxidation (Doelling et al 2002; Hanaoka et al 2002; Bassham et al 2006; Chung et al 2009; Hofius et al 2011; Yoshimoto 2012)
A rice autophagy-defective mutant, the OsATG7 tos-7 insertion line, is male-sterile owing to the inhibition of tapetum-cell degradation
Summary
In Arabidopsis and rice, a series of autophagyrelated (ATG) genes have been identified, as most of the essential residues are well conserved between yeasts and plants (Doelling et al 2002; Hanaoka et al 2002; Chung et al 2009; Xia et al 2011; Yoshimoto 2012). It functions in autophagic, or type II, programmed cell death (PCD) through hyperactivation in mammals and plants Apoptosis or type I PCD is involved in rapid responses, such as the hypersensitivity response to a pathogen, whereas autophagic PCD functions more slowly and is represented in leaf senescence
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