Abstract:

Arabidopsis contains five Brefeldin A‐inhibited guanine nucleotide exchange factors (BIGs), which play a critical role in vesicle biogenesis for protein traffic from the Golgi to the plasma membrane. Biological processes regulated by BIG1‐BIG4 are postulated to be distinct from those by BIG5. However, we show that the self‐pollinated BIG1^+/− big5 silique do not produce homozygous seeds, and some pollen tubes from BIG1^+/− big5 anthers grew slowly in vitro and failed to target nearby ovules in vivo. We identified the big1 big5 homozygote from the progeny of BIG1^+/− big5 plants transformed with BIG5, whose expression is driven by a pollen‐specific promoter pLat52, indicating that male gametophyte transmission is blocked in the double mutant. Confocal microscopy indicated that BIG1 and BIG5 are co‐localized in trans Golgi network. Thus, our data indicate that BIG1 and BIG5 are crucial for male gametophyte transmission.