Sea-island cotton (Gossypium barbadense L.) is one of the most valuable cotton species due to its silkiness, luster, long staples, and high strength, but its fiber development mechanism has not been surveyed comprehensively. We constructed a normalized fiber cDNA library (from -2 to 25 dpa) of G. barbadense cv. Pima 3-79 (the genetic standard line) by saturation hybridization with genomic DNA. We screened Pima 3-79 fiber RNA from five developmental stages using a cDNA array including 9,126 plasmids randomly selected from the library, and we selected and sequenced 929 clones that had different signal intensities between any two stages. The 887 high-quality expressed sequence tags obtained were assembled into 645 consensus sequences (582 singletons and 63 contigs), of which 455 were assigned to functional categories using gene ontology. Almost 50% of binned genes belonged to metabolism functional categories. Based on subarray analysis of the 887 high-quality expressed sequence tags with 0-, 5-, 10-, 15-, and 20-dpa RNA of Pima 3-79 fibers and a mixture of RNA of nonfiber tissues, seven types of expression profiles were elucidated. Furthermore our results showed that phytohormones may play an important role in the fiber development.

The early phase of phytohormone induction is a vital stage of somatic embryogenesis. This phase includes a key process for acquiring cellular totipotency through cellular dedifferentiation. To unravel the molecular mechanism of cellular dedifferentiation in cotton, we constructed a cDNA library using the suppression subtractive hybridization method. A total of 286 differential cDNA clones were sequenced and identified. Among these clones, 112 unique ESTs were significantly up-regulated during the early phase of phytohormone induction, and 40.2% of the ESTs were first identified. GST was highly expressed from 6 to 24 h after induction with phytohormone treatment. PRPs were predominantly expressed and exhibited distinct expression patterns in different treatments, suggesting that they are closely related to cellular dedifferentiation in cotton. Putative GhSAMS, GhSAMDC, GhSAHH and GhACO3 involvement in SAM metabolism was identified in this library. The analysis of qRT-PCR showed that two remarkable increased expressions of the four SAM-related genes happened during the early phase of phytohormone induction, and that a highly positive correlation existed between GhSAMS and GhSAHH. The highest expression level of GhSAMS might be associated with its reentry into the cell cycle. The histological observations further showed that some cells accomplished cellular dedifferentiation and division within 72 h in 2,4-D treatment, and that cellular dedifferentiation might be regulated through two alterations in SAM-dependent transmethylation activity in cotton. In addition, the expression patterns of differential genes in different treatments disclosed the complicated interaction between 2, 4-D and kinetin. cellular dedifferentiation, cotton, proline-rich protein, SAM-dependent transmethylation, suppression subtractive hybridization Cellular totipotency is an important phenomenon in nature, and plants are remarkable in that they can regenerate an entire plant from a small piece of tissue or even a single cell [1] . Cellular dedifferentiation involves acquiring cellular totipotency and is usually associated with reentry into the cell cycle (i.e., withdrawal from a differentiated state into a dedifferentiated cell state). That cells change their gene expression program is central to understand the process of cellular dedifferentiation [2] .Nagata analyzed the alteration of expression patterns of genes induced by phytohormone during the regaining of meristematic activity from differentiated tobacco cells; parA, parB and parC were identified [3] . Their protein products were subsequently proved to belong to the plant glutathione S-transferase (GST) family [4] . Some genes related to cellular dedifferentiation were isolated through studying alterations of gene expression programs, and those genes were identified to be associated with stress response, primary metabolism, cell wall synthesis or cell division [5,6] . For instance, cellular dedifferentiation of differentiated tobacco cells was shown to be accompanied by a sharp increase...