Identifi cation and expression profi le of GbAGL2, a C-class gene from Gossypium barbadense.

An AGAMOUS (AG)-like gene, GbAGL2, was isolated from Gossypium barbadense and characterized. Alignment and phylogenetic analysis indicated that GbAGL2 shared high homology with AG-subfamily genes and belonged to a C-class gene family. DNA gel blot analysis showed that GbAGL2 belonged to a low-copy gene family. Reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative real-time PCR (qPCR) revealed that GbAGL2 was highly expressed in reproductive tissues including ovules and carpels, but barely expressed in vegetative tissues. In addition, GbAGL2 expression in a cotton cultivar XuZhou142 (wt) (XZ142, G. hirsutum L.) and its fi breless mutant XZ142 (fl ) was examined. RNA in situ hybridization analysis indicated that GbAGL2 transcripts were preferentially restricted to outer ovule integuments, carpels and fi bres. These expression patterns implied that GbAGL2 might participate in the development of the carpel and ovule. Furthermore, Arabidopsis transformation was performed and modifi cations occurred in fl owers, and the silique length of transgenic plants also increased slightly, suggesting that the GbAGL2 gene may have a positive effect on the development of the ovary or ovule. Our fi ndings suggest that GbAGL2 might not only specify the identity of fl oral organs but also play a potential key role in ovary or fi bre development in cotton.

Overexpression of GbERF confers alteration of ethylene-responsive gene expression and enhanced resistance to Pseudomonas syringae in transgenic tobacco.

GbERF belongs to the ERF (ethylene responsive factor) family of transcription factors and regulates the GCC-box containing pathogen-related (PR) genes in the ethylene signal transduction pathway. To study the function of GbERF in the process of biotic stress, transgenic tobacco plants expressing GbERF were generated. Overexpression of GbERF did not change transgenic plant's phenotype and endogenous ethylene level. However, the expression profile of some ethylene-inducible GCC-box and non-GCC-box containing genes was altered, such as PR1b, PR2, PR3, PR4, Osmotin, CHN50, ACC oxidase and ACC synthase genes. These data indicate that the cotton GbERF could act as a transcriptional activator or repressor to regulate the differential expression of ethylene-inducible genes via GCC and non-GCC cis-elements. Moreover, the constitutive expression of GbERF in transgenic tobacco enhanced the plant's resistance to Pseudomonas syringae pv tabaci infection. In conclusion, GbERF mediates the expression of a wide array of PR and ethylene-responsive genes and plays an important role in the plant's response to biotic stress.