Genome-wide identification of the mitogen-activated protein kinase (MAPK) family in cotton (Gossypium hirsutum) reveals GhMPK6 involved in fiber elongation

Comprehensive analysis of MAPK gene family in upland cotton (Gossypium hirsutum) and functional characterization of GhMPK31 in regulating defense response to insect infestation

KEY MESSAGE

The transcriptomic, phenotypic and metabolomic analysis of transgenic plants overexpressing GhMPK31 in upland cotton revealed the regulation of H2O2 burst and the synthesis of defensive metabolites by GhMPK31. Mitogen-activated protein kinases (MAPKs) are a crucial class of protein kinases, which play an essential role in various biological processes in plants. Upland cotton (G. hirsutum) is the most widely cultivated cotton species with high economic value. To gain a better understanding of the role of the MAPK gene family, we conducted a comprehensive analysis of the MAPK gene family in cotton. In this study, a total of 55 GhMPK genes were identified from the whole genome of G. hirsutum. Through an investigation of the expression patterns under diverse stress conditions, we discovered that the majority of GhMPK family members demonstrated robust responses to abiotic stress, pathogen stress and pest stress. Furthermore, the overexpression of GhMPK31 in cotton leaves led to a hypersensitive response (HR)-like cell death phenotype and impaired the defense capability of cotton against herbivorous insects. Transcriptome and metabolomics data analysis showed that overexpression of GhMPK31 enhanced the expression of H2O2-related genes and reduced the accumulation of defensive related metabolites. The direct evidence of GhMPK31 interacting with GhRBOHB (H2O2-generating protein) were found by Y2H, BiFC, and LCI. Therefore, we propose that the increase of H2O2 content caused by overexpression of GhMPK31 resulted in HR-like cell death in cotton leaves while reducing the accumulation of defensive metabolites, ultimately leading to a decrease in the defense ability of cotton against herbivorous insects. This study provides valuable insights into the function of MAPK genes in plant resistance to herbivorous insects.

EB1C forms dimer and interacts with protein phosphatase 2A (PP2A) to regulate fiber elongation in upland cotton (Gossypium hirsutum)

Cotton is the most economically important natural fiber crop grown in more than sixty-five countries of the world. Fiber length is the main factor affecting fiber quality, but the existing main varieties are short in length and cannot suit the higher demands of the textile industry. It is necessary to discover functional genes that enable fiber length improvement in cotton through molecular breeding. In this study, overexpression of GhEB1C in Arabidopsis thaliana significantly promotes trichomes, tap roots, and root hairs elongation. The molecular regulation of GhEB1C involves its interactions with itself and GhB'ETA, and the function of GhEB1C regulation mainly depends on the two cysteine residues located at the C-terminal. In particular, the function activity of GhEB1C protein triggered with the regulation of protein phosphatase 2A, while silencing of GhEB1C in cotton significantly influenced the fiber protrusions and elongation mechanisms., Further, influenced the expression of MYB-bHLH-WD40 complex, brassinosteroids, and jasmonic acid-related genes, which showed that transcriptional regulation of GhEB1C is indispensable for cotton fiber formation and elongation processes. Our study analyzed the brief molecular mechanism of GhEB1C regulation. Further elucidated that GhEB1C can be a potential target gene to improve cotton fiber length through transgenic breeding.

A comprehensive overview of cotton genomics, biotechnology and molecular biological studies

Cotton is an irreplaceable economic crop currently domesticated in the human world for its extremely elongated fiber cells specialized in seed epidermis, which makes it of high research and application value. To date, numerous research on cotton has navigated various aspects, from multi-genome assembly, genome editing, mechanism of fiber development, metabolite biosynthesis, and analysis to genetic breeding. Genomic and 3D genomic studies reveal the origin of cotton species and the spatiotemporal asymmetric chromatin structure in fibers. Mature multiple genome editing systems, such as CRISPR/Cas9, Cas12 (Cpf1) and cytidine base editing (CBE), have been widely used in the study of candidate genes affecting fiber development. Based on this, the cotton fiber cell development network has been preliminarily drawn. Among them, the MYB-bHLH-WDR (MBW) transcription factor complex and IAA and BR signaling pathway regulate the initiation; various plant hormones, including ethylene, mediated regulatory network and membrane protein overlap fine-regulate elongation. Multistage transcription factors targeting CesA 4, 7, and 8 specifically dominate the whole process of secondary cell wall thickening. And fluorescently labeled cytoskeletal proteins can observe real-time dynamic changes in fiber development. Furthermore, research on the synthesis of cotton secondary metabolite gossypol, resistance to diseases and insect pests, plant architecture regulation, and seed oil utilization are all conducive to finding more high-quality breeding-related genes and subsequently facilitating the cultivation of better cotton varieties. This review summarizes the paramount research achievements in cotton molecular biology over the last few decades from the above aspects, thereby enabling us to conduct a status review on the current studies of cotton and provide strong theoretical support for the future direction.

Revealing Genetic Differences in Fiber Elongation between the Offspring of Sea Island Cotton and Upland Cotton Backcross Populations Based on Transcriptome and Weighted Gene Coexpression Networks

Fiber length is an important indicator of cotton fiber quality, and the time and rate of cotton fiber cell elongation are key factors in determining the fiber length of mature cotton. To gain insight into the differences in fiber elongation mechanisms in the offspring of backcross populations of Sea Island cotton Xinhai 16 and land cotton Line 9, we selected two groups with significant differences in fiber length (long-fiber group L and short-fiber group S) at different fiber development stages 0, 5, 10 and 15 days post-anthesis (DPA) for transcriptome comparison. A total of 171.74 Gb of clean data was obtained by RNA-seq, and eight genes were randomly selected for qPCR validation. Data analysis identified 6055 differentially expressed genes (DEGs) between two groups of fibers, L and S, in four developmental periods, and gene ontology (GO) term analysis revealed that these DEGs were associated mainly with microtubule driving, reactive oxygen species, plant cell wall biosynthesis, and glycosyl compound hydrolase activity. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis indicated that plant hormone signaling, mitogen-activated protein kinase (MAPK) signaling, and starch and sucrose metabolism pathways were associated with fiber elongation. Subsequently, a sustained upregulation expression pattern, profile 19, was identified and analyzed using short time-series expression miner (STEM). An analysis of the weighted gene coexpression network module uncovered 21 genes closely related to fiber development, mainly involved in functions such as cell wall relaxation, microtubule formation, and cytoskeletal structure of the cell wall. This study helps to enhance the understanding of the Sea Island–Upland backcross population and identifies key genes for cotton fiber development, and these findings will provide a basis for future research on the molecular mechanisms of fiber length formation in cotton populations.

The involvement of gaseous signaling molecules in plant MAPK cascades: function and signal transduction

This review describes the interaction of gaseous signaling molecules and MAPK cascade components, which further reveals the specific mechanism of the crosstalk between MAPK cascade components and gaseous signaling molecules. Plants have evolved complex and sophisticated mitogen-activated protein kinase (MAPK) signaling cascades that are engaged in response to environmental stress. There is currently compelling experimental evidence that gaseous signaling molecules are involved in MAPK cascades. During stress, nitric oxide (NO) activates MAPK cascades to transmit stimulus signals, and MAPK cascades also regulate NO biosynthesis to mediate NO-dependent physiological processes. Activated MAPK cascades lead to phosphorylation of specific sites of aminocyclopropane carboxylic acid synthase to regulate the ethylene biosynthesis-signaling pathway. Hydrogen sulfide functions upstream of MAPKs and regulates the MAPK signaling pathway at the transcriptional level. Here, we describe the function and signal transduction of gaseous signaling molecules involved in MAPK cascades and focus on introducing and discussing the recent data obtained in this field concerning the interaction of gaseous signaling molecules and MAPK cascades. In addition, this article outlines the direction and challenges of future work and further reveals the specific mechanism of the crosstalk between MAPK cascade components and gaseous signaling molecules.