Cloning and expression of a cDNA encoding ribosomal protein S4 from Rice (Oryza sativa)

Identification of photoperiod-regulated gene in soybean and functional analysis in Nicotiana benthamiana

Soybean (Glycine max) is a short-day crop and the photoperiod is a crucial factor regulating its flowering time. To investigate the molecular mechanism controlling the flowering time by photoperiod in soybean, cDNA-amplified fragment length polymorphism (cDNA-AFLP) was used to identify photoperiod-regulated genes in leaves of soybean growing under short-day length, neutral photoperiod and long-day length. A total of 36 transcript-derived fragments (TDFs) were identified to be regulated by photoperiod. Among them, 26 TDFs were homologues of genes with known function. These genes are involved in secondary metabolism, cellular metabolism, cell wall components metabolism, ion transport and hormone signalling. Silencing of the homologue genes in Nicotiana benthamiana for 14 TDFs was conducted by virus-induced gene silencing. The flowering time was delayed by silencing of the genes encoding rhodanese and 40S ribosomal protein S4 (RPS4). The results indicated that rhodanese and RPS4 probably play important roles in regulating flowering time.

Genetic diversity of the natural populations of Arabidopsis thaliana in China

Although extensive studies have been conducted on the genetic structure of Arabidopsis thaliana (A. thaliana) populations worldwide, the populations from China have never been studied. In this study, we collected 560 individuals from 19 natural populations of A. thaliana distributed in East China along the lower reaches of the Yangtze River, and two populations from northwest China (Xinjiang Province). We adopted two kinds of molecular marker, inter-simple sequence repeats (ISSRs) and random amplified polymorphic DNA (RAPDs) to investigate the genetic diversity within and among populations, and the correlation between the genetic and geographic distances. Thirteen ISSR primers produced 165 polymorphic bands (PPB) (96%) and 11 RAPD primers produced 162 polymorphic bands (98%) in about 560 individuals. The two marker systems generated similar patterns of genetic diversity in these natural populations. The AMOVA analysis indicated about 42-45% of the total genetic variation existed within populations, and found possible geographic structure. The Mantel test revealed a significant correlation between the geographic distance and the genetic distance of these populations in general. A close genetic relationship was found among four populations in the Jiangxi Province, and these always appeared clustered together as a monophyletic group in unweighted pair-group method with arithmetic averages dendrograms based on both ISSR and RAPD data sets. Based on the observation of recolonization and extinction of naturally distributed populations of A. thaliana, and the pattern of their genetic differentiation, the distribution of this species in China might be a result of natural dispersal under the strong influence of human activity.

The Great Wall of China: a physical barrier to gene flow?

One population from each of six plant species along both sides of the Juyong-guan Great Wall, together with one population from each of five species along both sides of a path on a mountain top near Juyong-guan, were selected to study the effect of the Great Wall as a barrier on genetic differentiation between two subpopulations using RAPD markers. Significant genetic differentiation was found between the subpopulations on both sides of the Great Wall. A wind-pollinated woody species, Ulmus pumila, showed less genetic differentiation than four insect-pollinated species: Prunus armeniaca, Ziziphus jujuba, Vitex negundo, and Heteropappus hispidus. Cleistogenes caespitosa, a wind-pollinated perennial herb, displayed more genetic differentiation between subpopulations than the insect-pollinated species because of its propagation strategy. Although AMOVA analysis showed that subpopulations divided by a mountain path had diverged genetically, the variance component between the subpopulations on both sides of the Great Wall was significantly larger than that between the subpopulations at the control site. Therefore, it is reasonable to deduce that the Juyong-guan Great Wall has served as a physical barrier to gene flow between subpopulations separated for more than 600 years.