Abstract
Sorghum is a self-pollinated crop with multiple economic uses as cereal, forage, and biofuel feedstock. Hybrid breeding is a cornerstone for sorghum improvement strategies that currently relies on cytoplasmic male sterile lines. To engineer genic male sterility, it is imperative to examine the genetic components regulating anther/pollen development in sorghum. To this end, we have performed transcriptomic analysis from three temporal stages of developing anthers that correspond to meiotic, microspore and mature pollen stages. A total of 5286 genes were differentially regulated among the three anther stages with 890 of them exhibiting anther-preferential expression. Differentially expressed genes could be clubbed into seven distinct developmental trajectories using K-means clustering. Pathway mapping revealed that genes involved in cell cycle, DNA repair, regulation of transcription, brassinosteroid and auxin biosynthesis/signalling exhibit peak expression in meiotic anthers, while those regulating abiotic stress, carbohydrate metabolism, and transport were enriched in microspore stage. Conversely, genes associated with protein degradation, post-translational modifications, cell wall biosynthesis/modifications, abscisic acid, ethylene, cytokinin and jasmonic acid biosynthesis/signalling were highly expressed in mature pollen stage. High concurrence in transcriptional dynamics and cis-regulatory elements of differentially expressed genes in rice and sorghum confirmed conserved developmental pathways regulating anther development across species. Comprehensive literature survey in conjunction with orthology analysis and anther-preferential accumulation enabled shortlisting of 21 prospective candidates for in-depth characterization and engineering male fertility in sorghum.
Highlights
Sorghum is a self-pollinated crop with multiple economic uses as cereal, forage, and biofuel feedstock
Hybrid production in sorghum exclusively relies on the CMS system where male sterile line is crossed with an identical male fertile line leading to hybrids with sterile seeds
Rice orthologs of several other genes in this group are involved in regulating key aspects of anther development including chromosome pairing and synapsis (Completion of meiosis[1]; OsCOM1, Central region component 1; OsCRC1, OsSGO1 and Homologous Pairing Aberration in Rice Meiosis 3; PAIR3), meiotic crossover (Meiotic chromosome association[1]; MEICA1, RPA1c, ZEP1 and OsMSH5), pollen wall development (Cytochrome P450 Hydroxylase 704B2; CYP704B2, LTPL44, CYP703A3, ATP Binding Cassette G26; OsABCG26, Polyketide synthase[2]; OsPKS2 and UDP-arabipyranose mutase[3]; UDP-arabinopyranose mutase 3 (UAM3)), anther wall development (HTH1 (Hothead1)), meiotic regulation (MEL2), and tapetum degeneration (STRL-like[2]; OsSTRL2, Acyl CoA synthatase[12]; OsACOS12, and Defective Tapetum Cell Death[1]; DTC1) (Table 1)
Summary
Sorghum is a self-pollinated crop with multiple economic uses as cereal, forage, and biofuel feedstock. Rice orthologs of several other genes in this group are involved in regulating key aspects of anther development including chromosome pairing and synapsis (Completion of meiosis[1]; OsCOM1, Central region component 1; OsCRC1, OsSGO1 and Homologous Pairing Aberration in Rice Meiosis 3; PAIR3), meiotic crossover (Meiotic chromosome association[1]; MEICA1, RPA1c, ZEP1 and OsMSH5), pollen wall development (Cytochrome P450 Hydroxylase 704B2; CYP704B2, LTPL44, CYP703A3, ATP Binding Cassette G26; OsABCG26, Polyketide synthase[2]; OsPKS2 and UDP-arabipyranose mutase[3]; UAM3), anther wall development (HTH1 (Hothead1)), meiotic regulation (MEL2), and tapetum degeneration (STRL-like[2]; OsSTRL2, Acyl CoA synthatase[12]; OsACOS12, and Defective Tapetum Cell Death[1]; DTC1) (Table 1).
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