H3K36 methyltransferase GhKMT3;1a and GhKMT3;2a promote flowering in upland cotton

Abstract

Abstract Background SET DOMAIN GROUP (SDG) proteins act as histone lysine methyltransferases, which play pivotal roles in a variety of developmental processes, such as flowering determination, by modifying chromatin structure to regulate related gene transcription. Although there is extensive evidence that histone methylation plays a key role in plant growth and development, especially H3K36 methylation in Arabidopsis, little information is available for cotton. Results A total of 86 SDG genes were identified through genome-wide analysis of the Gossypium hirsutum genome. Subsequently, we thoroughly studied Arabidopsis, G. arboreum, and G. raimondii homologs and conducted a comprehensive analysis of their gene structure and conserved domain organization. A total of 12 conserved domains were detected in 86 GhSDGs and classified into seven main classes to clarify their evolutionary relationship, which was unevenly distributed across 25 chromosomes of G. hirsutum. Transcriptome data analysis of tissue and developmental stage expression showed that the GhSDG gene was expressed in different tissues, with high expression levels in the flowering stage and floral organs such as stamens and pistils, especially for KMT3 classes involved in activation of flowering, showing dramatically changed expression patterns. Subsequently, we performed reverse transcription-quantitative PCR for 8 KMT3 classes of GhSDGs in eight tissues (root, stem, leaf, sepal, petals, bud, stamens and pistils). In addition, two predicted GhSDG genes (GhKMT3;1a and GhKMT3;2a) were shown to regulate cotton development by virus-induced gene silencing. Budding and flowering were delayed in upland cotton plants with silenced GhKMT3;1a and GhKMT3;2a, and plant height was also lowered. We found that GhKMT3;1a and GhKMT3;2a-mediated H3K36 methylation regulates the expression of flowering-related genes and plays an important role in the flowering of upland cotton. Conclusion We comprehensively identified 86 GhSDG genes in upland cotton. Our data indicate that GhKMT3;1a and GhKMT3;2a-mediated H3K36 methylation regulate the expression of flowering-related genes and play an important role in the growth and development of cotton plants. These findings may also lay a foundation for breeding early-maturing cotton varieties in the future.