MALE STERILE6021 (MS6021) is required for the development of anther cuticle and pollen exine in maize

Abstract

The anther cuticle and pollen wall function as physical barriers that protect genetic material from various environmental stresses. The anther cuticle is composed of wax and cutin, the pollen wall includes exine and intine, and the components of the outer exine are collectively called sporopollenin. Other than cuticle wax, cutin and sporopollenin are biopolymers compounds. The precise constituents and developmental mechanism of these biopolymeric are poorly understood. Here, we reported a complete male sterile mutant, male sterile6021, in maize. The mutant displayed a smooth anther surface and irregular pollen wall formation before anthesis, and its tapetum was degraded immaturely. Gas chromatography-mass spectrometry analysis revealed a severe reduction of lipid derivatives in the mutant anther. We cloned the gene by map based cloning. It encoded a fatty acyl carrier protein reductase that was localized in plastids. Expression analysis indicated that MS6021 was mainly expressed in the tapetum and microspore after the microspore was released from the tetrad. Functional complementation of the orthologous Arabidopsis mutant demonstrated that MS6021 is conserved between monocots and dicots and potentially even in flowering plants. MS6021 plays a conserved, essential role in the successful development of anther cuticle and pollen exine in maize.

Wheat ms5 male‐sterility is induced by recessive homoeologous A and D genome non‐specific lipid transfer proteins

“…() and Tian et al . (), have shown the importance of exine development for pollen viability. Among these, Lou et al .…”

“…Numerous studies, such as Quilichini et al (2015), Choi et al (2011), Chen et al (2011 and Tian et al (2017), have shown the importance of exine development for pollen viability. Among these, Lou et al (2014) found that knockout of AtTEK, which is involved in nexine formation, resulted in the absence of nexine, no intine and male-sterility in Arabidopsis thaliana.…”

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

“…We hypothesize that delayed PCD of the inner four anther layers in ms305, including tapetum cells, leads to the degradation of pollen grains, and this should be responsible for its complete male sterility. Lipids play an important role in regulating plant anther development, a large number of studies have reported the role of fatty acids and their derivatives in regulating anther fertility [15,29,42]. For example, anther cuticle, including cutin and wax, can protect plant anthers from hydration [26].…”

“…For example, anther cuticle, including cutin and wax, can protect plant anthers from hydration [26]. In maize, MS45, MS26, MS30, MS33, IPE1, and APV1 are reported to participate in the aliphatic metabolic pathways, which are required for anther cuticle development [19,26,29,39,43]. The abortion characteristics of MS30, MS33, IPE1, and APV1 in maize were described, such as the swollen microspore and the decreased vacuole of APV1 at the vacuolated stage [19], severe degradation of the tapetum in IPE1 [20] and an obvious abortion of MS30 first appeared after the vacuolated stage [15], these were, however, different from ms305.…”

“…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].…”