Wu Mi, Xu Zhiyong, Fu Chao, Wang Nian, Zhang Ruiting, Le Yu, Chen Meilin, Yang Ningyu, Li Yuanxue, Zhang Xianlong, Li Ximei, Lin Zhongxu
National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070 Hubei, China.
Shandong Key Laboratory of Dryland Farming Technology, Shandong Engineering Research Center of Germplasm Innovation and Utilization of Salt-Tolerant Crops, College of Agronomy, Qingdao Agricultural University, Qingdao 266109 Shandong, China.
J Adv Res. 2025 Feb 17. doi: 10.1016/j.jare.2025.02.022.
Fiber strength is a critical determinant of fiber quality, with stronger fibers being highly preferred in the cotton textile industry. However, the genetic basis and the specific regulatory mechanism underlying the formation of cotton fiber strength remain largely unknown.
To explore fiber strength-related genes, QTL mapping, map-based cloning, and gene function verification were conducted in a backcross inbred line BS41 derived from interspecific hybridization between upland cotton and sea-island cotton.
Upland cotton Emian22 (E22) and an interspecific backcross inbred line (BIL) BS41 were used as parents to construct secondary segregation populations for BSA and QTL mapping of fiber strength. The candidate gene GbNTL9 was identified through map-based cloning and expression analysis. The function of NTL9 was determined through transgenic experiments and cytological observations. The regulatory mechanisms of NTL9 were explored using RNA-seq, RT-qPCR, yeast two-hybrid, bimolecular fluorescence complementation, and yeast one-hybrid.
A major QTL for fiber strength, qFS-A11-1, was mapped to a 14.6-kb genomic region using segregating populations from E22 × BS41. GbNTL9, which encodes a NAC transcription factor, was identified as the candidate gene. Overexpression of both upland cotton genotype NTL9 and sea-island genotype NTL9 in upland cotton enhanced fiber strength by facilitating the dense accumulation and orderly organization of cellulose microfibrils within the cell wall. Transcriptomic analysis revealed that NTL9 inhibited the expression of genes involved in secondary wall synthesis, such as CESA4, CESA7, and CESA8, thereby delaying cell wall cellulose deposition and altering the microfibril deposition pattern. NTL9 interacted with MYB6 and functioned as a downstream gene in the ethylene signaling pathway. Additionally, an effective gene marker NTL9-24 was developed to distinguish haplotypes from G. barbadense and G. hirsutum for fiber quality breeding program.
Our findings demonstrate that GbNTL9 positively regulates fiber strength through altering the microfibril deposition pattern, and provide a new insight into the molecular mechanism underlying fiber strength.
纤维强度是纤维品质的关键决定因素，在棉纺织工业中，更强的纤维备受青睐。然而，棉花纤维强度形成的遗传基础和具体调控机制仍 largely 未知。
为探究与纤维强度相关的基因，在陆地棉与海岛棉种间杂交衍生的回交自交系 BS41 中进行了 QTL 定位、图位克隆及基因功能验证。
以陆地棉鄂棉 22（E22）和一个种间回交自交系（BIL）BS41 为亲本，构建用于纤维强度 BSA 和 QTL 定位的次级分离群体。通过图位克隆和表达分析鉴定出候选基因 GbNTL9。通过转基因实验和细胞学观察确定 NTL9 的功能。利用 RNA-seq、RT-qPCR、酵母双杂交、双分子荧光互补和酵母单杂交探究 NTL9 的调控机制。
利用 E22×BS41 的分离群体，将一个纤维强度主效 QTL，qFS-A11-1 定位到一个 14.6kb 的基因组区域。编码 NAC 转录因子的 GbNTL9 被鉴定为候选基因。陆地棉基因型 NTL9 和海岛棉基因型 NTL9 在陆地棉中的过表达均通过促进细胞壁内纤维素微纤丝的密集积累和有序排列来增强纤维强度。转录组分析表明，NTL9 抑制参与次生壁合成的基因如 CESA4、CESA7 和 CESA8 的表达，从而延迟细胞壁纤维素沉积并改变微纤丝沉积模式。NTL9 与 MYB6 相互作用并在乙烯信号通路中作为下游基因发挥作用。此外，开发了一个有效的基因标记 NTL9-24，用于在纤维品质育种计划中区分海岛棉和陆地棉的单倍型。
我们的研究结果表明，GbNTL9 通过改变微纤丝沉积模式正向调控纤维强度，并为纤维强度的分子机制提供了新的见解。
