Arabidopsis AtBECLIN 1/AtAtg6/AtVps30 is essential for pollen germination and plant development

Abstract

Pollen germination on the surface of compatible stigmatic tissues is an essential step for plant fertilization. Here we report that the Arabidopsis mutant bcl1 is male sterile as a result of the failure of pollen germination. We show that the bcl1 mutant allele cannot be transmitted by male gametophytes and no homozygous bcl1 mutants were obtained. Analysis of pollen developmental stages indicates that the bcl1 mutation affects pollen germination but not pollen maturation. Molecular analysis demonstrates that the failure of pollen germination was caused by the disruption of AtBECLIN 1. AtBECLIN 1 is expressed predominantly in mature pollen and encodes a protein with significant homology to Beclin1/Atg6/Vps30 required for the processes of autophagy and vacuolar protein sorting (VPS) in yeast. We also show that AtBECLIN 1 is required for normal plant development, and that genes related to autophagy, VPS and the glycosylphosphatidylinositol anchor system, were affected by the deficiency of AtBECLIN 1.

The Arabidopsis Phosphatidylinositol 3-Kinase Is Important for Pollen Development

“…causes cell death at the tricellular stage in Arabidopsis pollen (Gupta et al, 2002). BECLIN1, an Arabidopsis homolog of yeast Beclin1/Atg6/Vps30, which associates with VPS34 and plays a role in autophagy and vacuolar protein sorting, is expressed predominantly in mature pollen, and disruption of this gene by T-DNA insertion results in male sterility due to severely reduced pollen germination (Fujiki et al, 2007;Qin et al, 2007). VACUOLESS1 (VPS16) and POKY POLLEN TUBE (VPS52), Arabidopsis VPS homologs, also play roles in pollen tube elongation (Hicks et al, 2004;Lobstein et al, 2004).…”

The autophagy gene,ATG18a, plays a negative role in powdery mildew resistance and mildew-induced cell death in Arabidopsis

“…[8][9][10] In plants, several atg mutants have been shown to display early senescence and/or spontaneous cell death in nutrient deficient or even in nutrient-rich conditions. 8,9,[11][12][13][14][15][16][17][18] Recently, we showed that atg2, atg5, atg7 and atg10 exhibited early senescence and spontaneous cell death under nutrient rich conditions. 1 In addition, we showed that these mutants displayed enhanced disease resistance to the powdery mildew pathogen, G. cichoracearum.…”

Beclin1: A role in membrane dynamics and beyond

“…In Arabidopsis thaliana, ATG6 disruption affects pollen germination and male fertility. 98,99 In support of an autophagy-independent function of ATG6 is the finding that none of the previously examined plant ATG mutants exhibit male gametophytic defects. 98,99 However, ATG6 deficiency apparently alters the expression of numerous genes, including some that are involved in autophagic signaling, suggesting the possible involvement of ATG proteins other than ATG6 in the process of pollen germination.…”