Abstract
Silencing phytochrome A1 gene (PHYA1) by RNA interference in Upland cotton (Gossypium hirsutum L. cv. Coker 312) had generated PHYA1 RNAi lines with improved fiber quality (longer, stronger and finer fiber). To reveal molecular mechanisms that govern fiber development with positive fiber traits, a study of global gene expression profiling of 10-DPA fibers in a PHYA1 RNAi line and its parent Coker 312 was conducted by high-throughput RNA sequencing. A comparative analysis of transcriptomes between the two lines had identified 142 genes that were differentially expressed in the 10-DPA fiber of the RNAi line. Gene Ontology analysis showed that these differentially expressed genes were mainly involved in metabolic pathways, heterocyclic/organic cyclic compound binding and multiple enzyme activities, and cell structures which were reported to play important roles in fiber development. Twenty-eight KEGG pathways were mapped for the 142 genes, and the pathways related to glycolysis/gluconeogenesis and pyruvate metabolism were the most abundant and followed by cytochrome P450-involved pathways, suggesting that fiber improvement could be through the regulation of proteins involved in cytochrome P450 pathways. Genes encoding WRKY transcription factors, sucrose synthase, xyloglucan endotransglucosylase hydrolase, udp-glucuronate: xylan alpha-glucuronosyltransferase, and genes involved in lipid metabolism and ABA/brassinosteroid signal transduction pathways were found differentially expressed in the RNAi line. These genes have direct impacts on cotton fiber quality. The results of this study elucidate molecular signatures and possible mechanisms of fiber improvement in the background of PHYA1 RNAi in cotton and should help for future fine-tuning and programming of cotton fiber development.
Highlights
Cotton is the most important textile fiber and an important oilseed crop [1], providing significant economic impact as a major cash crop in 70 counties around the world [2]
To reveal molecular mechanisms that govern fiber development with positive fiber traits, a study of global gene expression profiling of 10-days post anthesis (DPA) fibers in a phytochrome A1 gene (PHYA1) RNAi line and its parent Coker 312 was conducted by high-throughput RNA sequencing
Twenty-eight KEGG pathways were mapped for the 142 genes, and the pathways related to glycolysis/gluconeogenesis and pyruvate metabolism were the most abundant and followed by cytochrome P450-involved pathways, suggesting that fiber improvement could be through the regulation of proteins involved in cytochrome P450 pathways
Summary
Cotton is the most important textile fiber and an important oilseed crop [1], providing significant economic impact as a major cash crop in 70 counties around the world [2]. The cotton industry demands to produce cotton with good fiber qualities, including longer and finer fiber with high fiber strength. Most of these desirable fiber traits are controlled by many genes (QTLs) and are very difficult to improve simultaneously by conventional breeding program because some of these traits are inversely related. Cotton fiber is a single cell derived from the epidermal layer of the ovule of a cotton seed, and its development consists of four overlapping stages: initiation, elongation (primary wall biosynthesis), secondary wall biosynthesis and maturation [3]. As the fiber approaches the end of elongation, the major phase of secondary wall synthesis starts [3]
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