AP1G2 Affects Mitotic Cycles of Female and Male Gametophytes in Arabidopsis

Yongmei Zhou; Wenqin Fang; Ziqin Pang; Li-Yu Chen; Hanyang Cai; Noor-Ul- Ain; Men-Chi Chang; Ray Ming

doi:10.3389/fpls.2022.924417

AP1G2 Affects Mitotic Cycles of Female and Male Gametophytes in Arabidopsis

Front Plant Sci. 2022 Jul 7:13:924417. doi: 10.3389/fpls.2022.924417. eCollection 2022.

Authors

Yongmei Zhou^{1

2}, Wenqin Fang^{1

2}, Ziqin Pang^{1

2}, Li-Yu Chen^{1

2}, Hanyang Cai^{1

2}, Noor-Ul- Ain^{1

2}, Men-Chi Chang³, Ray Ming⁴

Affiliations

¹ FAFU and UIUC Joint Center for Genomics and Biotechnology, Key Laboratory of Sugarcane Biology and Genetic Breeding Ministry of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, China.
² Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Fujian Agriculture and Forestry University, Fuzhou, China.
³ Department of Agronomy, National Taiwan University, Taipei, Taiwan.
⁴ Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States.

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.

Keywords: AP1G2; Arabidopsis; Ca2+ signaling; PICALM proteins; gametogenesis.