Cotton is an important natural fiber crop worldwide which plays a vital role in our daily life.  High yield is a constant goal of cotton breeding, and lint percentage (LP) is one of the important components of cotton fiber yield.  A stable QTL controlling LP, qLP_A01.1, was identified on chromosome A01 from Gossypium hirsutum introgressed lines with G. tomentosum chromosome segments in a previous study.  To fine-map qLP_A01.1, an F₂ population with 986 individuals was established by crossing G. hirsutum cultivar CCRI35 with the chromosome segment substitution line HT_390.  A high-resolution genetic map including 47 loci and spanning 56.98 cM was constructed in the QTL region, and qLP_A01.1 was ultimately mapped into an interval corresponding to an ~80 kb genome region of chromosome A01 in the reference genome, which contained six annotated genes.  Transcriptome data and sequence analysis revealed that S-acyltransferase protein 24 (GoPAT24) might be the target gene of qLP_A01.1.  This result provides the basis for cotton fiber yield improvement via marker-assisted selection (MAS) and further studies on the mechanism of cotton fiber development.

Naturally colored cotton (NCC) represents a kind of eco-friendly and sustainable textile material. Limited colors and inferior yield and quality are the major obstacles to the wide application of NCCs.  The present work aimed to generate new colored cotton by synthesizing and accumulating anthocyanins in fibers.  Two anthocyanin regulatory genes Lc and GhPAP1D were fused and specifically expressed in fibers of the secondary cell wall (SCW) stage.  The transgenic fibers exhibited pronounced purplish-red color at 20 to 30 DPA (days post anthesis), and reddish-brown color at maturation.  Meanwhile, expressing Lc and GhPAP1D led to reduced elongation rate and impaired SCW deposition in fibers, finally decreased fiber strength and length, and low lint percentage at maturation.  Metabolomic and transcriptomic analyses indicated that the whole flavonoid pathway was significantly up-regulated, and multiple flavonoids, including anthocyanins, proanthocyanidins and flavonols, were accumulated in developing and mature fibers.  It was also found that lignin biosynthesis and accumulation were significantly increased in fibers of the SCW synthesis stage.  Our results provided a feasible strategy to promote anthocyanin synthesis and accumulation in cotton fibers, and also its side effects on fiber coloration and development, which laid the foundation for future NCC color innovation.