AP1G2 Affects Mitotic Cycles of Female and Male Gametophytes in Arabidopsis

Abstract

During sexual reproduction in flowering plants, haploid spores are formed from meiosis of spore mother cells. The spores then undergo mitosis, develop into female and male gametophytes, and give rise to seeds after fertilization. We identified a female sterile mutant ap1g2-4 from EMS mutagenesis, and analyses of two T-DNA insertion mutants, ap1g2-1+/− and ap1g2-3−/−, and detected a partial female and male sterility. The ap1g2 mutant gametophyte development was arrested at one nuclear stage. A complementation test using a genomic sequence of AP1G2 with its native promoter restored the function in the three ap1g2 mutant lines. Transcriptome profiling of ap1g2 ovules revealed that four genes encoding clathrin assembly proteins PICALM5A/B and PICALM9A/B, which were involved in endocytosis, were downregulated, which were confirmed to interact with AP1G2 through yeast two-hybrid assays and BIFC analysis. Our result also demonstrated that RALFL4-8-15-19-26 CML16 and several calcium-dependent protein kinases, including CPK14-16-17, were all downregulated in the ovules of ap1g2-1+/−. Moreover, Ca2+ concentration was low in impaired gametophytes. Therefore, we proposed that through interaction with PICALM5A/B and PICALM9A/B, AP1G2 may mediate gametogenesis accompanied by Ca2+ signaling in Arabidopsis. Our findings revealed a crucial role of AP1G2 in female and male gametogenesis in Arabidopsis and enhanced our understanding of the molecular mechanisms underpinning sexual reproduction in flowering plants.

Male gametogenesis in flowering plants

“…Arabidopsis AP1G2 is an adaptor protein complex 1 (AP-1) γ subunit and interacts with PICALM5A/B and PICALM9A/B, mediating endocytosis in transporting insoluble enzymes and membrane proteins from the trans-Golgi network (TGN) to endosomes and lysosomes. In the ap1g2-1 +/− mutant, nearly half of the microspores failed to undergo mitosis due to defective polarization (Zhou et al, 2022). Arabidopsis importin β, KETCH1 (karyopherin enabling transport of cytoplasmic HYL1), is located in the nucleus of the reproductive cells at unicellular and bicellular pollen (Xiong et al, 2020).…”

Genomic mechanisms and consequences of diverse postzygotic barriers between monkeyflower species

“…Nevertheless, sex-independent incompatibility loci have been identified in tomato (Rick 1966), rice (Sano 1990;Koide et al 2008b), lettuce (Giesbers et al 2018) and yellow monkeyflowers (Kerwin and Sweigart 2017). Because core cellular processes such as meiosis and mitosis are critical for gametogenesis in both sexes (Drews et al 1998), many of the same genes are essential in both sexes (Drews and Yadegari 2002;Ma et al 2021;Yu et al 2022;Zhou et al 2022). Thus, breakdown of these processes in hybrids could cause sex-independent incompatibility.…”

Multiple, single trait GWAS and supervised machine learning reveal the genetic architecture ofFraxinus excelsiortolerance to ash dieback in Europe

“…The second of the three SNPs is located within a region encoding a wall-associated receptor kinase-like 20 protein; homologs of this gene are part of the pattern triggered immunity (PTI) system, a conserved plant defence system which recognises conserved components of plant pathogens and triggers an immune response (Jones & Dangl, 2006). The third and final coding domain SNP was located on an AP-1 complex subunit gamma-2-like gene which in Arabidopsis is critical for the development of male and female gametophytes (Zhou et al, 2022). Table 2.…”