Genetic variation in MYB5_A12 is associated with fibre initiation and elongation in tetraploid cotton

The MYB gene family, which is predominantly composed of the R2R3-MYB family, is large and functionally diverse in plants including cotton (Gossypium hirsutum L.) (Guan et al., 2014; Tian and Zhang, 2021; Walford et al., 2011; Wan et al., 2016; Wang et al., 2019; Wu et al., 2018). In Arabidopsis, the R2R3-MYB protein AtMYB5, which belongs to the GL1 branch in the phylogenetic tree, is a component of the MYB-bHLH-WD40 protein complex that directly regulates the expression of GL2 to control the fate of seed coat outer epidermal cells and plant hairs (Gonzalez et al., 2009). However, the role of the homolog of AtMYB5 in cotton is currently unknown.