First report of Protokeelia spinifera and Rhopalodia iriomotensis from China,with comments on their systematic positions

Protokeelia is described as a new and rare pennate diatom genus in China. Its valve includes two parts： ventral valve and dorsal valve. The ventral valve is more or less convex or concave. The raphe runs in a distinct elevated and thickened siliceous ridge. In the internal valve, beneath the raphe are fibulae or fibulae clusters which connect the ventral and dorsal valves. One species, P. spinifera Round ＆ Basson, is observed in the water samples from a mangrove forest in Sai Kung, Hong Kong, China. Its main morphological features are described in this paper along with electron microscope （EM） photos. Morphological comparisons are also made among several allied species. In addition, a newly recorded species for China, Rhopalodia iriomotensis Kobayasi, Nagumo ＆ Tanaka, is discussed here. Because several key features observed in this species resemble those of some Protokeelia species, we suggest that it may actually represent a Protokeelia species.

Expression pattern of GASA,downstream genes of DELLA,in Arabidopsis

Separation and functional research of related components involved in gibberellins(GAs) signaling are important to clarify the mechanism of GA functioning.Research on the downstream components of DELLA,the key factor of the GA signaling pathway,is limited at present.GASA(GA-Stimulated in Arabidopsis) family contains 15 genes usually regulated by GA in Arabidopsis thaliana.All GASA proteins have a cleavable signal peptide in N terminus and a conserved GASA domain including 12 cysteines in C terminus.RT-PCR analysis revealed that the expression of GASA4 and GASA6 were down-regulated,but GASA1 and GASA9 were up-regulated in the DELLA mutants,gai-t6 and rga-24,as well as the double mutant,consisting with the results that GASA4 and GASA6 were induced,but GASA1 and GASA9 were inhibited by exogenous GA3.In addition,the expression patterns of other GASA genes were regulated by GA and ABA,separately or cooperatively.Most of GASA genes were expressed in roots,stems,leaves,flowers and developing siliques.GUS gene driven by the promoters of GASA6,GASA7,GASA8,GASA9,GASA10,GASA11 and GASA12 were used as reporters and it was found that all GASA genes expressed in the growing and differentiating organs and abscission zones,suggesting the role of these genes in cell growth and differentiation.This study provided an important basis for functional study of the GASA gene family in the GA and ABA signaling pathway.

Ectopic Expression of FaDREB2 Enhances Osmotic Tolerance in Paper Mulberry

Dehydration-responsive element binding （DREB） proteins are a subfamily of AP2/ERF transcription factors that have been shown to improve tolerance to osmotic stresses in plants. To improve the osmotic stress tolerance of paper mulberry （Broussonetia papyrifera L. Vent）, an economically important tree, we transformed it with a plasmid carrying tall fescue （Festuca arundinacea Schreb） FaDREB2 under the control of CaMV 35S. The ectopic expression of FaDREB2 did not cause growth retardation, and the paper mulberry seedlings expressing FaDREB2 showed higher salt and drought tolerance than wild-type plants （WT）. After 13 d of withholding water, or 15 d in the presence of 250 mM NaCI, all the WT plants died, while the plants expressing FaDREB2 survived. The FaDREB2 transgenic plants had higher leaf water and chlorophyll contents, accumulated more proline and soluble sugars, and had less membrane damage than the WT plants under high salt and water-deficient conditions. Taken together, the results indicate the feasibility of improving tolerance to multiple environmental stresses in paper mulberry seedlings via genetic engineering, by introducing FaDREB2, which promotes the increased accumulation of osmolytes （soluble sugars and proline）, to counter osmotic stresses caused by abiotic factors.