Cotton is one of the most important textile crops but little is known how microRNAs regulate cotton fiber development. Using a well-studied cotton fiberless mutant Xu-142-fl, we compared 54 miRNAs for their expression between fiberless mutant and its wildtype. In wildtype Xu-142, 26 miRNAs are involved in cotton fiber initiation and 48 miRNAs are related to primary wall synthesis and secondary wall thickening. Thirty three miRNAs showed different expression in fiber initiation between Xu-142 and Xu-142-fl. These miRNAs potentially target 723 protein-coding genes, including transcription factors, such as MYB, ARF, and LRR. ARF18 was newly predicted targets of miR160a, and miR160a was expressed at higher level in −2DPA of Xu-142-fl compared with Xu-142. Furthermore, the result of Gene Ontology-based term classification (GO), EuKaryotic Orthologous Groups (KOG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis shows that miRNA targets were classified to 222 biological processes, 64 cellular component and 42 molecular functions, enriched in 22 KOG groups, and classified into 28 pathways. Together, our study provides evidence for better understanding of miRNA regulatory roles in the process of fiber development, which is helpful to increase fiber yield and improve fiber quality.

Cotton (Gossypium hirsutum L.) is one of the most important cash crops worldwide. Cytoplasmic male sterility (CMS) is an excellent breeding system for exploitation of heterosis, which has great potential to increase crop yields. To understand the molecular mechanism of CMS in cotton, we compared transcriptome, cytomorphological, physiological and bioinformatics data between the CMS line C2P5A and its maintainer line C2P5B. By using high-throughput sequencing technology, 178,166 transcripts were assembled and 2013 differentially expression genes (DEGs) were identified at three different stages of C2P5A anther development. In this study, we identified DEGs associated with reactive oxygen species (ROS), peroxisomes, aldehyde dehydrogenases (ALDH), cytochrome oxidase subunit VI, and cytochrome P450, and DEGs associated with tapetum development, Jojoba acyl-CoA reductase-related male sterility protein, basic helix-loop-helix (bHLH) and MYB transcription factors. The abnormal expression of one of these genes may be responsible for the CMS C2P5A line. In gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, DEGs were mainly related to carbohydrate metabolism, amino acid metabolism, transport and catabolism, and signal transduction. Carbohydrate metabolism provides energy for anther development, starch and sucrose metabolism, fatty acid biosynthesis and metabolism and ascorbate and aldarate metabolism. These results showed that numerous genes and multiple complex metabolic pathways regulate cotton anther development. Weighted correlation network analysis (WGCNA) indicated that three modules, ‘turquoise,’ ‘blue,’ and ‘green,’ were specific for the CMS C2P5A line. The ‘turquoise’ and ‘blue’ modules were mainly related to carbohydrate metabolism, amino acid metabolism, energy metabolism, peroxisomes, pyruvate metabolism as well as fatty acid degradation. The ‘green’ module was mainly related to energy metabolism, carbon metabolism, translation, and lipid metabolism. RNA-sequencing and WGCNA polymerization modules were screened for key genes and pathways related to CMS in cotton. This study presents a new perspective for further research into the metabolic pathways of pollen abortion in the CMS C2P5A line and also provides a theoretical basis for its breeding and production.

Coronatine [COR] is a novel type of plant growth regulator with similarities in structure and property to jasmonate. The objective of this study was to examine the relationship between increased root vitality induced by 10nM COR and reactive oxygen species scavenging under potassium (K)-replete (2.5mM) and K-deficient (0.05mM) conditions in hydroponic cultured cotton seedlings. K-replete and K-deficient conditions increased root vitality by 2.7- and 3.5-fold, respectively. COR treatment significantly decreased lipid peroxidation in cotton seedlings determined by reduction in MDA levels. These results suggest that COR improves the functioning of both enzymatic and non-enzymatic antioxidant systems. Under K-replete and K-deficient conditions, COR significantly increased the activities of antioxidant enzymes SOD (only for K-repletion), CAT, GPX, and APX comparing; COR also significantly increased DPPH-radical scavenging activity. However, COR led to 1.6- and 1.7-fold increases in superoxide anion (O₂^•-) concentrations, and 5.7- and 2.1-fold increases in hydrogen peroxide (H₂O₂) levels, respectively. Additionally, COR intensified the DAB staining of H₂O₂ and the NBT staining of O₂^•-. Therefore, our results reveal that COR-induced ROS accumulation stimulates the activities of most antioxidant enzymes but does not induce oxidative stress in cotton roots.