Genetic Mapping and Characteristics of Genes Specifically or Preferentially Expressed during Fiber Development in Cotton

Cotton fiber is an ideal model to study cell elongation and cell wall construction in plants. During fiber development, some genes and proteins have been reported to be specifically or preferentially expressed. Mapping of them will reveal the genomic distribution of these genes, and will facilitate selection in cotton breeding. Based on previous reports, we designed 331 gene primers and 164 protein primers, and used single-strand conformation polymorphism (SSCP) to map and integrate them into our interspecific BC1 linkage map. This resulted in the mapping of 57 loci representing 51 genes or proteins on 22 chromosomes. For those three markers which were tightly linked with quantitative trait loci (QTLs), the QTL functions obtained in this study and gene functions reported in previous reports were consistent. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of 52 polymorphic functional primers showed that 21 gene primers and 17 protein primers had differential expression between Emian22 (Gossypium hirsutum) and 3–79 (G. barbadense). Both RT-PCR and quantitative real-time PCR (qRT-PCR) analyses of the three markers tightly linked with QTLs were consistent with QTL analysis and field experiments. Gene Ontology (GO) categorization revealed that almost all 51 mapped genes belonged to multiple categories that contribute to fiber development, indicating that fiber development is a complex process regulated by various genes. These 51 genes were all specifically or preferentially expressed during fiber cell elongation and secondary wall biosynthesis. Therefore, these functional gene-related markers would be beneficial for the genetic improvement of cotton fiber length and strength.棉花纤维是研究植物细胞伸长及细胞壁构建的理想模式材料。在纤维发育过程中，已有研究报道部分基因与蛋白质会出现特异性或偏好性表达。对这些分子开展定位分析，可揭示相关基因的基因组分布特征，同时有助于棉花育种中的性状选择工作。基于既往研究报道，我们设计了331对基因引物与164对蛋白质引物，并借助单链构象多态性（single-strand conformation polymorphism, SSCP）技术进行定位分析，将其整合至本研究构建的种间BC1连锁图谱中。最终成功定位了57个基因座，涵盖51个基因或蛋白质，分布于22条染色体上。对于3个与数量性状位点（quantitative trait loci, QTLs）紧密连锁的分子标记，本研究获得的QTL功能与既往文献报道的基因功能具有一致性。针对52对具有多态性的功能引物开展逆转录聚合酶链式反应（reverse transcription-polymerase chain reaction, RT-PCR）分析，结果显示，21对基因引物与17对蛋白质引物在鄂棉22（Emian22，Gossypium hirsutum）与3–79（G. barbadense）之间存在差异表达。针对这3个与QTL紧密连锁的标记开展RT-PCR与实时荧光定量聚合酶链式反应（quantitative real-time PCR, qRT-PCR）分析，结果均与QTL定位分析及田间试验结果一致。基因本体（Gene Ontology, GO）分类分析显示，51个已定位基因几乎均隶属于调控纤维发育的多个功能类别，表明纤维发育是一个受多基因协同调控的复杂生物学过程。这51个基因均在纤维细胞伸长与次生壁合成阶段呈现特异性或偏好性表达。因此，这些基于功能基因开发的分子标记将有助于棉花纤维长度与强度的遗传改良。