Genetics and evolution of MIXTA genes regulating cotton lint fiber development

Abstract

Cotton, with cellulose-enriched mature fibers, is the largest source of natural textiles. Through a map-based cloning strategy, we isolated an industrially important lint fiber development gene (Li ) that encodes an MYB-MIXTA-like transcription factor (MML) on chromosome D12 (GhMML4_D12). Virus-induced gene silencing or decreasing the expression of the GhMML4_D12 gene in n NSM plants resulted in a significant reduction in epidermal cell prominence and lint fiber production. GhMML4_D12 is arranged in tandem with GhMML3, another MIXTA gene responsible for fuzz fiber development. These two very closely related MIXTA genes direct fiber initiation production in two specialized cell forms: lint and fuzz fibers. They may control the same metabolic pathways in different cell types. The MIXTAs expanded in Malvaceae during their evolution and produced a Malvaceae-specific family that regulates epidermal cell differentiation, different from the gene family that regulates leaf hair trichome development. Cotton has developed a unique transcriptional regulatory network for fiber development. Characterization of target genes regulating fiber production has provided insights into the molecular mechanisms underlying cotton fiber development and has allowed the use of genetic engineering to increase lint yield by inducing more epidermal cells to develop into lint rather than fuzz fibers.

Core cis‐element variation confers subgenome‐biased expression of a transcription factor that functions in cotton fiber elongation

“…Transcriptome sequencing has repeatedly demonstrated that a high fraction (often 20–40%) of genes in G. hirsutum exhibit A‐ or D‐subgenome biased expression (Yoo & Wendel, ; Liu et al ., ; Zhang et al ., ). In particular, in G. hirsutum the myeloblastosis (MYB)‐MIXTA‐like transcription factor gene GhMML4 ( GhMML4_D12 ), a key regulator of lint (spinnable fiber) development, shows a strong subgenome‐biased expression (Wu et al ., ). We speculate that that selection has shaped gene expression variation through its action on underlying variation in multiple regulatory elements throughout the genome.…”

Unraveling Cotton Fiber Development Using Fiber Mutants in the Post‐Genomic Era

“…Long lint fibers (>10 mm) can be easily separated from seeds through the ginning process. Recent studies indicated that both lint and fuzz fibers may share common developmental pathways at least in early differentiation, despite being under different genetic controls (Turley and Kloth, 2002;Wan et al, 2014Wan et al, , 2016Wu et al, 2018;Zhu et al, 2018). Fuzz fibers initiate ?3 to 5 DPA (Stewart, 1975;Wan et al, 2016) and stop elongating ?10 DPA.…”

“…A recessive n 2 locus was discovered in 1947 (Ware et al, 1947). Musaev and Abzalov (1972) to be controlled by two loci, n 2 and li 3 , that regulate fuzz and lint fiber initiation, respectively (Zhang and Pan, 1991;Wu et al, 2018). A recent study indicated that the fuzzless phenotype in G. barbadense is mainly due to the presence of the n 2 gene (Zhu et al, 2018).…”

“…Further genetic analysis concluded that GhMML3_A12 (Gh_A12G1503) is the N 1 gene. The fiberless line XZ142 fl does not have the N 1 gene but n 2 according to Zhang and Pan (1991) and Wu et al (2018). Virus-induced gene silence of GhMML3_A12 in cotton resulted in a fuzzless or reduced fuzz phenotype, but not a fiberless phenotype as seen in the transgenic cottons reported by Walford et al (2011).…”

“…There are at least 10 MMLs identified in the cotton genome (Bedon et al, 2014;Wu et al, 2018). There are at least 10 MMLs identified in the cotton genome (Bedon et al, 2014;Wu et al, 2018).…”