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Plant trichomes originate from epidermal cells. In this work, we demonstrated that a homeodomain-leucine zipper (HD-Zip) gene, Gh_A06G1283 (GhHD-1A), was related to the leaf trichome trait in allotetraploid cotton and could be a candidate gene for the T1 locus. The ortholog of GhHD-1A in the hairless accession Gossypium barbadense cv. Hai7124 was interrupted by a long terminal repeat (LTR) retrotransposon, while GhHD-1A worked well in the hairy accession Gossypium hirsutum acc. T586. Sequence and phylogenetic analysis showed that GhHD-1A belonged to the HD-Zip IV gene family, which mainly regulated epidermis hair development in plants. Silencing of GhHD-1A and its homoeologs GhHD-1D in allotetraploid T586 and Hai7124 could significantly reduce the density of leaf hairs and affect the expression levels of other genes related to leaf trichome formation. Further analysis found that GhHD-1A mainly regulated trichome initiation on the upper epidermal hairs of leaves in cotton, while the up-regulated expression of GhHD-1A in different organs/tissues also altered epidermal trichome development. This study not only helps to unravel the important roles of GhHD-1A in regulating trichome initiation in cotton, but also provides a reference for exploring the different forms of trichome development in plants.

Cotton Verticillium wilt is a serious soil-borne disease that leads to significant losses in fiber yield and quality worldwide. Currently, the most effective way to increase Verticillium wilt resistance is to develop new resistant cotton varieties. Lines 5026 and 60182 are two Verticillium wilt-resistant upland cotton accessions. We previously identified a total of 25 quantitative trait loci (QTLs) related to Verticillium wilt resistance from 5026 and 60182 by assembling segregating populations from hybridization with susceptible parents. In the current study, using 13 microsatellite markers flanking QTLs related to Verticillium wilt resistance, we developed 155 cotton inbred lines by pyramiding different QTLs related to Verticillium wilt resistance from a filial generation produced by crossing 5026 and 60182. By examining each allele's effect and performing multiple comparison analysis, we detected four elite QTLs/alleles (q-5/NAU905-2, q-6/NAU2754-2, q-8/NAU3053-1 and q-13/NAU6598-1) significant for Verticillium wilt resistance, pyramiding these elite alleles increased the disease resistance of inbred lines. Furthermore, we selected 34 elite inbred lines, including five lines simultaneously performing elite fiber quality, high yield and resistance to V. dahliae, 14 lines with elite fiber quality and disease resistance, three lines with high yield and disease resistance, and 12 lines with resistance to V. dahliae. No correlation between Verticillium wilt resistance and fiber quality traits/yield and its components was detected in the 155 developed inbred lines. Our results provide candidate markers for disease resistance for use in marker-assisted breeding (MAS), as well as elite germplasms for improving important agronomic traits via modern cotton breeding.

The cytochrome P450 (CYP) superfamily is the largest enzymatic protein family in plants, and it also widely exists in mammals, fungi, bacteria, insects and so on. Members of this superfamily are involved in multiple metabolic pathways with distinct and complex functions, playing important roles in a vast array of reactions. As a result, numerous secondary metabolites are synthesized that function as growth and developmental signals or protect plants from various biotic and abiotic stresses. Here, we summarize the characterization of CYPs, as well as their phylogenetic classification. We also focus on recent advances in elucidating the roles of CYPs in mediating plant growth and development as well as biotic and abiotic stresses responses, providing insights into their potential utilization in plant breeding.