Cotton grown in the United States are day-length insensitive annuals and are grown under long-day summers. Photoperiod sensitivity, present in tropical wild and landraces endemic to the center of origin and diversity, is a major barrier for the introgression of tropical gene pool into the US cotton. Previously, we mapped the major photoperiod response locus Gb_Ppd1 on chromosome D06 of Pima cotton (Gossypium barbadense L.). In the current study, an F₂ population of 2112 gametes was used to fine map the Gb_Ppd1 locus. Two sequence-tagged-site and nine kompetitive allele-specific polymerase chain reaction (KASP) markers were developed and the Gb_Ppd1 locus was fine mapped to 1.1 cM region flanked by novel markers 17-KASP-8, 17-KASP-10, and 15-PR-10A. The closely linked markers identified 2.10 Mb region in the G. barbadense genome that contained 18 putative gene sequences. A candidate gene Gbar_D06G014560 showed high homology to VASCULAR PLANT ONE ZINC FINGER PROTEIN 1 involved in photoperiodism in Arabidopsis. We evaluated the diagnostic polymorphisms for the flanking markers on a diversity panel of 91 Pima accessions. These markers would be useful in marker-assisted selection of photoperiod response in cotton breeding. Further, quantitative gene expression analysis indicated that the CONSTANS (CO)/FLOWERING LOCUS T (FT) system is conserved in the photoperiod response pathway in Pima cotton, while CO and FT are likely not the causal genes underlying flowering time at the Gb_Ppd1 locus. The Gb_Ppd1 gene may be an upstream regulatory sequence in the FT gene pathway that controls photoperiodism in photoperiod-sensitive cotton by affecting the CO/FT interaction under long-day-length conditions.

中文翻译：

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皮马棉（Gossypium barbadense L.）光周期敏感基因（GB_PPD1）的精细定位和靶向基因组分析


美国种植的棉花是对日照不敏感的一年生植物，在长日照的夏季下生长。光周期敏感性存在于起源和多样性中心特有的热带野生品种和地方品种中，是热带基因库渗入美国棉花的主要障碍。此前，我们将主要光周期响应位点Gb_Ppd1定位在皮马棉（Gossypium barbadense L.）染色体D06上。在当前的研究中，使用 2112 个配子的 F ₂ 群体来精细绘制 Gb_Ppd1 基因座。开发了两个序列标记位点和九个竞争性等位基因特异性聚合酶链反应 (KASP) 标记，并将 Gb_Ppd1 基因座精细定位到两侧为新标记 17-KASP-8、17-KASP-10 和 15 的 1.1 cM 区域-PR-10A。紧密连锁的标记在海岛 G. barbadense 基因组中识别出 2.10 Mb 的区域，其中包含 18 个假定的基因序列。候选基因Gbar_D06G014560与拟南芥中参与光周期现象的维管植物一锌指蛋白1表现出高度同源性。我们评估了 91 个皮马种质多样性组中侧翼标记的诊断多态性。这些标记可用于棉花育种中光周期响应的标记辅助选择。此外，定量基因表达分析表明，CONSTANS (CO)/FLOWERING LOCUS T (FT) 系统在皮马棉的光周期响应途径中是保守的，而 CO 和 FT 可能不是 Gb_Ppd1 位点开花时间的致病基因。 Gb_Ppd1基因可能是FT基因途径中的上游调控序列，通过影响长日照条件下的CO/FT相互作用来控制光周期敏感棉花的光周期。