Genome-wide identification of cotton CrRLK1L family genes and potential function of GhCrRLK1L104 in cell elongation

Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) proteins play important roles in cell growth, plant morphogenesis, reproduction, hormone signaling, plant immunity and stress responses in Arabidopsis. However, not much information is available about their functions in cotton. We identified a total of 125, 73 and 71 full-length putative CrRLK1L genes in G. hirsutum, G. arboreum and G. raimondii, which are much greater than that of the other plants. The phylogenetic and gene structure analysis divided the cotton CrRLK1L genes into six major groups, among which only group I and II contained AtCrRLK1Ls of Arabidopsis. Genome collinearity analysis revealed large scale reciprocal translocations on chromosome 2 among Gossypium A genomes species, which led to uneven distribution of CrRLK1L genes on this chromosome. In addition, transcriptome data combined with qRT-PCR analysis showed some GhCrRLK1Ls were preferentially expressed in fibers during the specific stages of ovules or fibers development. Notably, GhCrRLK1L104 was highly expressed in fibers at 30 days post anthesis, and the GhCrRLK1L104::GFP fusion protein was located on the plasma membrane. Furthermore, overexpression of the GhCrRLK1L104 gene in Arabidopsis increased the trichomes length of the rosette leaves, indicated its vital roles in cell elongation. These results provided a strong foundation to further explore the molecular mechanism of CrRLK1L genes in upland cotton in cell elongation, that can be used in future cotton breeding program.