Cisandtransregulatory divergence underlies phenotypic and evolutionary diversification. Relatively little is understood about the complexity of regulatory evolution accompanying crop domestication, particularly for polyploid plants. Here, we compare the fiber transcriptomes between wild and domesticated cotton (Gossypium hirsutum) and their reciprocal F₁hybrids, revealing genome-wide (~15%) and often compensatorycisandtransregulatory changes under divergence and domestication. The high level oftransevolution (54%–64%) observed is likely enabled by genomic redundancy following polyploidy. Our results reveal that regulatory variation is significantly associated with sequence evolution, inheritance of parental expression patterns, co-expression gene network properties, and genomic loci responsible for domestication traits. With respect to regulatory evolution, the two subgenomes of allotetraploid cotton are often uncoupled. Overall, our work underscores the complexity of regulatory evolution during fiber domestication and may facilitate new approaches for improving cotton and other polyploid plants.

Increasing levels of UV‐B radiation caused by the greenhouse effect has become an emerging threat to crop health and yield. The glutathione (GSH) metabolic pathway is generally involved in plant stress responses through scavenging accumulated reactive oxygen species, and is therefore believed to play an essential role in enhancing plant tolerance to UV‐B stress. However, the complex evolutionary details of this pathway in polyploid plants, especially under UV‐B stress, remain largely unknown. Here, using the important allotetraploid crop, Gossypium hirsutum , as an example, we comprehensively investigated the composition and phylogenetic relationships of genes encoding 12 key structural enzymes in this pathway, and compared the expression changes of all the relevant genes under UV‐B stress (16 kJ m ⁻² d ⁻¹ ) based on six leaf transcriptomes. Consequently, we identified 205 structural genes by genome‐wide searching and predicted 98 potential regulatory genes under multiple stress conditions by co‐expression network analysis. Furthermore, we revealed that 19 structural genes including 5 homoeologous pairs and 96 regulatory genes possessing 25 homoeologous pairs were reticulately correlated without homoeologous selection preference under UV‐B stress. This result suggests a complex rewiring and reassignment between structural genes and their regulatory networks in the duplicated metabolic pathways of polyploid cotton. This study extends our understanding of the molecular dynamics of the GSH metabolic pathway in response to UV‐B stress in G. hirsutum and, more broadly, in polyploid plants.

Objective: This study aimed to screen the differentially expressed genes (DEGs) of Gossypium hirsutum under UV-B stress and identify the significant pathways based on gene enrichment analysis results.Methods: In this study, the allotetraploid crop G. hirsutum was used to examine changes in various physiological indexes under UV-B stress, and screened out all DEGs under UV-B stress (16 kJ m^-2 d^-1) based on six leaf transcriptomes. The main enrichment pathways of DEGs were analyzed according to gene annotation. Finally, we predicted the regulatory genes of phenylpropanoid pathway under UV-B stress by co-expression network analysis, and selected GhMYB4 for verification.Results: Gene annotation analysis revealed that DEGs were predominantly enriched in pathways related to photosynthesis and secondary metabolism. Further analysis revealed that UV-B stress impaired photosynthesis mainly by damaging photosystem II (PSII) and inhibiting electron transport, whereas G. hirsutum responded to UV-B stress by synthesizing secondary metabolites such as anthocyanins and lignin. We selected the regulatory genes GhMYB4 for verification. It was found to be an anthocyanin negative regulator in response to UV-B stress.Conclusions: UV-B stress impaired photosynthesis mainly by damaging photosystem II (PSII) and inhibiting electron transport, whereas G. hirsutum responded to UV-B stress by synthesizing secondary metabolites such as anthocyanins and lignin.