Nitrogen and mepiquat chloride can affect fiber quality and cotton yield

Molecular Regulation of Cotton Fiber Development: A Review

Cotton (Gossypium spp.) is an economically important natural fiber crop. The quality of cotton fiber has a substantial effect on the quality of cotton textiles. The identification of cotton fiber development-related genes and exploration of their biological functions will not only enhance our understanding of the elongation and developmental mechanisms of cotton fibers but also provide insights that could aid the cultivation of new cotton varieties with improved fiber quality. Cotton fibers are single cells that have been differentiated from the ovule epidermis and serve as a model system for research on single-cell differentiation, growth, and fiber production. Genes and fiber formation mechanisms are examined in this review to shed new light on how important phytohormones, transcription factors, proteins, and genes linked to fiber development work together. Plant hormones, which occur in low quantities, play a critically important role in regulating cotton fiber development. Here, we review recent research that has greatly contributed to our understanding of the roles of different phytohormones in fiber development and regulation. We discuss the mechanisms by which phytohormones regulate the initiation and elongation of fiber cells in cotton, as well as the identification of genes involved in hormone biosynthetic and signaling pathways that regulate the initiation, elongation, and development of cotton fibers.

The effects of mepiquat chloride (DPC) on the soluble protein content and the activities of protective enzymes in cotton in response to aphid feeding and on the activities of detoxifying enzymes in aphids

BACKGROUND

Mepiquat chloride (DPC) enhances the resistance of cotton plants, and it is widely used as a growth regulator. DPC can stimulate photosynthesis, stabilize the structure of cotton leaves, and affect population reproduction and energy substances in Aphis gossypii Glover (cotton aphids), but interactions between DPC and cotton aphids remain unclear. In this study, we analyzed the physiological responses of cotton to DPC, and the toxicity of DPC toward cotton aphids, before and after feeding, to explore the DPC-induced defense mechanism against cotton aphids.

RESULTS

Measurements of protective enzyme activity in cotton showed that the soluble protein contents, peroxidase (POD) activity, and catalase (CAT) activity in cotton treated with different concentrations of DPC were higher than in the control. Superoxide dismutase (SOD) activity was higher than that of the control when the concentration of DPC was < 0.1 g/L. Under aphid feeding stress, POD activity in cotton treated with a low insect population density was significantly lower than in the controls, but the reverse was true for cotton treated with a high insect population density, and SOD activity was positively correlated with population density. The activities of detoxification enzymes in field and laboratory experiments showed that DPC promoted the specific activity of glutathione S-transferase (GST) in cotton aphids, while the specific activities of carboxylesterase (CarE) and acetylcholinesterase (AchE) were decreased.

CONCLUSIONS

DPC enhanced the aphid resistance in cotton by increasing the soluble protein content and the activity of protective enzymes. It also had a toxic effect on cotton aphids by increasing GST activity (the main DPC target). DPC increased the soluble protein content and protective enzymes activity in cotton under aphid stress, and thereby enhanced tolerance to cotton aphids. It conclude that DPC interferes with cotton aphids through indirect (DPC induced cotton defense responses) and direct (DPC toxicity to cotton aphids) ways, which plays a positive role in interfering with cotton aphids.

Understanding the role of phytohormones in cotton fiber development through omic approaches; recent advances and future directions

Cotton is among the most important fiber crops for the textile-based industry, thanks to its cellulose-rich mature fibers. The fiber initiation and elongation are one of the best models for deciphering mechanisms of single-cell differentiation and growth, that also target of fiber development programs. During the last couple of decades, high yielding omics approaches (genomics, transcriptomics, and proteomics), have helped in the identification of several genes and gene products involved in fiber development along with functional relationship to phytohormones. For example, MYB transcription factor family and Sus gene family have been evidenced by controlling cotton fiber initiation. Most importantly, the biosynthesis, responses, and transporting of phytohormones is documented to participate in the initiation of cotton fibers. Herein, in this review, the reliable genetic evidence by manipulating the above genes in cotton have been summarized to describe the relationships among key phytohormones, transcription factors, proteins, and downstream fiber growth-related genes such as Sus. The effect of other important factors such as ROS, fatty acid metabolism, and actin (globular multi-functional proteins) over fiber development has also been discussed. The challenges and deficiencies in the research of cotton fiber development have been mentioned along with a future perspective to discover new crucial genes using multiple omics analysis.