ABNORMAL POLLEN VACUOLATION1 (APV1) is required for male fertility by contributing to anther cuticle and pollen exine formation in maize

Abstract

Anther cuticle and pollen exine are the major protective barriers against various stresses. The proper functioning of genes expressed in the tapetum is vital for the development of pollen exine and anther cuticle. In this study, we report a tapetum-specific gene, Abnormal Pollen Vacuolation1 (APV1), in maize that affects anther cuticle and pollen exine formation. The apv1 mutant was completely male sterile. Its microspores were swollen, less vacuolated, with a flat and empty anther locule. In the mutant, the anther epidermal surface was smooth, shiny, and plate-shaped compared with the three-dimensional crowded ridges and randomly formed wax crystals on the epidermal surface of the wild-type. The wild-type mature pollen had elaborate exine patterning, whereas the apv1 pollen surface was smooth. Only a few unevenly distributed Ubisch bodies were formed on the apv1 mutant, leading to a more apparent inner surface. A significant reduction in the cutin monomers was observed in the mutant. APV1 encodes a member of the P450 subfamily, CYP703A2-Zm, which contains 530 amino acids. APV1 appeared to be widely expressed in the tapetum at the vacuolation stage, and its protein signal co-localized with the endoplasmic reticulum (ER) signal. RNA-Seq data revealed that most of the genes in the fatty acid metabolism pathway were differentially expressed in the apv1 mutant. Altogether, we suggest that APV1 functions in the fatty acid hydroxylation pathway which is involved in forming sporopollenin precursors and cutin monomers that are essential for the development of pollen exine and anther cuticle in maize.

Genus-wide sequencing supports a two-locus model for sex-determination in Phoenix

“…Specifically, mutants of Phoenix sex determination Page nr. 10 of 26 CYP703 in rice 21 and maize 29 and GPAT3 in rice 24 revealed their function in both pollen formation and/or anther development through their indispensable role in various lipid synthesis pathways. In rice, GPAT3 and CYP703A are expressed in tapetal cells 24,30 which are responsible for synthesis and secretion of sporopollenin precursors, a major component of the outer pollen cell wall 31 .…”

Naming CRISPR alleles: endonuclease-mediated mutation nomenclature across species

“…The number corresponds to the serial number of all mutations in the given gene. For example, ms10-CRISPR1 represents the CRISPR1 mutation in the male sterile 10 gene (Somaratne et al 2017). There is no requirement to include CRISPR in the allele symbol as a part of the laboratory line number or name.…”

“…(2013), Straimer et al (2012), reviewed in Singer and Frischknecht (2017) RoundwormCRISPR, TALEN, ZFNreviewed in Gaj et al (2013), Waaijers and Boxem (2014) Sea squirtCRISPR, TALEN, ZFNKawai et al (2012), Sasaki et al (2014), Treen et al (2014) SilkwormCRISPR, TALEN, ZFNReviewed in Xu and O’Brochta (2015)Plants BarleyCRISPR, TALENLawrenson et al (2015), Wendt et al (2013) BunchgrassTALENShang et al (2013a) CabbageCRISPR, TALENLawrenson et al (2015), Sun et al (2013) CornCRISPR, TALEN, ZFNChar et al (2015), Shukla et al (2009), Somaratne et al (2017) ChlamydomonasCRISPR, ZFNShin et al (2016), Sizova et al (2013) Duncan grapefruitCRISPRJia et al (2016) LiverwortCRISPRSugano et al (2014) PetuniaCRISPR, ZFNMarton et al (2010), Zhang B et al (2016a, b, c) RiceCRISPR, TALENLi et al (2012), reviewed in Belhaj et al (2013) SorghumCRISPRJiang et al (2013) SoybeanCRISPR, TALEN, ZFNCurtin et al (2011), Haun et al (…”

Male sterile 305 Mutation Leads the Misregulation of Anther Cuticle Formation by Disrupting Lipid Metabolism in Maize

“…However, only a handful of these genes have been cytologically characterized, and even fewer male sterile genes have been isolated. Moreover, over 50 GMS mutants in maize have been identified and characterized with the majority being recessive, such as ZmMs7 [9], Ms8 [10], Ms9 [11], Ms22/Msca1 [12], Ms23 [13], Ms26 [14], Ms30 [15], Ms32 [16], ZmMs33 [17], Ms45 [18], APV1 [19], IPE1 [20], MAC1 [21], and OCL4 [22]. The cloning and functional characterization of some male sterile genes have significantly contributed to our understanding of the molecular mechanisms of anther and pollen development in maize, which might provide useful genetic resources for hybrid maize seed production.…”

“…The main lipid precursors of sporopollenin include linear fatty acids and monomers of oxygen-containing aromatic compounds, such as coumarin (C9) and ferulic acid (C10), all of which are synthesized in the tapetum cells [26]. In recent years, many genes that are involved in fatty acid metabolism and mediating anther cuticle and sporopollenin formation, whose mutation often leads to male sterile in Arabidopsis thaliana, rice and maize have been reported [19,29,30]. In addition, phospholipase a (releases lysophospholipids) and lipoxygenase (catalyses fatty acid oxidation) were involved in regulating pollen germination in olive (Olea europaea L.) [31].…”