Characterization of the XTH gene family in cotton
Zusammenfassung
Cotton is the single most important crop in Texas agriculture, reaching a value of 4 billion dollars per year. Cotton fiber is the major product in cotton cultivation which is converted into economic revenue. Therefore, most research groups have focused on fiber development and improvement of fiber quality.
The xyloglucan endotransglucosylase/hydrolase gene family has a unique role in plant cell wall elongation and development during plant growth. It can cut and paste xyloglucan fragments into xyloglucan hemicellulose matrix in Type I plant cell wall, allowing cell wall extension and loosening while bearing tension for normal cell metabolism. XTH genes encode enzymes that may play a role in determining fiber length and other fiber qualities during cotton fiber development. Both the structures and functions of the XTH family have been well studied in Arabidopsis.
In this research the cotton XTH genes were cloned by using the sequence information of Arabidopsis XTHs. A cotton boll cDNA library and a cotton genomic BAC library were screened and used for cotton XTH gene cloning. The clones of cotton XTHs were classified to three distinctive groups based on their 3ŒUTR sequences. The three groups were denoted as GhXTH-G1, G2, and G3. The sequences of abnormal transcripts of GhXTH-G1 showed transcription termination in the middle of introns, producing shortened forms of mRNAs. In addition, two GhXTH-G1 genes were analyzed and assigned to A and D sub genomes. Real time quantitative RT-PCR was used to study tissue and development specific patterns of XTH gene expression. GhXTH-G3 appears to be the most important cotton XTHs in cotton fiber development. Also, hormone treatment results indicated that brassinolide (BL), gibberellin (GA3), naphthalene acetic acid (NAA) induced GhXTH expression in developing cotton fiber.