Arabidopsis ADP‐RIBOSYLATION FACTOR‐A1s mediate tapetum‐controlled pollen development

Abstract

SUMMARY Propagation of angiosperms mostly relies on sexual reproduction, in which gametophytic development is a pre‐requisite. Male gametophytic development requires both gametophytic and sporophytic factors, most importantly early secretion and late programmed cell death of the tapetum. In addition to transcriptional factors, proteins at endomembrane compartments, such as receptor‐like kinases and vacuolar proteases, control tapetal function. The cellular machinery that regulates their distribution is beginning to be revealed. We report here that ADP‐RIBOSYLATION FACTOR‐A1s (ArfA1s) are critical for tapetum‐controlled pollen development. All six ArfA1s in the Arabidopsis genome are expressed during anther development, among which ArfA1b is specific to the tapetum and developing microspores. Although the ArfA1b loss‐of‐function mutant showed no pollen defects, probably due to redundancy, interference with ArfA1s by a dominant negative approach in the tapetum resulted in tapetal dysfunction and pollen abortion. We further showed that all six ArfA1s are associated with the Golgi and the trans‐Golgi network/early endosome, suggesting that they have roles in regulating post‐Golgi trafficking to the plasma membrane or to vacuoles. Indeed, we demonstrated that the expression of ArfA1bDN interfered with the targeting of proteins critical for tapetal development. The results presented here demonstrate a key role of ArfA1s in tapetum‐controlled pollen development by mediating protein targeting through post‐Golgi trafficking routes.

An Update on the Key Factors Required for Plant Golgi Structure Maintenance

“…Arabidopsis genome encodes six highly conserved Arf1 proteins share at least 97% sequence identity, suggesting their function redundancy ( Xu and Scheres, 2005 ; Singh et al, 2018 ). All six Arf1s associates with Golgi/TGN ( Zhu et al, 2021 ) and have been implicated in various trafficking steps including trafficking from the ER to the Golgi, vacuolar trafficking and endocytosis/recycling ( Singh and Jurgens, 2018 ). The fungal toxin brefeldin A (BFA) is known as a potent inhibitor of Arf-GEFs.…”

“…One factor restricting the Golgi research, especially the molecular mechanism of Golgi structure maintenance is the functional redundancy of expanded members in a particular protein family, such as Arf1s, SNAREs, and Rabs ( Pinheiro et al, 2009 ; Rui et al, 2021 ; Zhu et al, 2021 ). Disruption of single gene of those families usually leads to mild or even no phenotype.…”