Xicun Dong

Linear energy transfer dependence of the effects of carbon ion beams on adventitious shoot regeneration from in vitro leaf explants of Saintpaulia ionahta

Purpose: To determine the effects of carbon ion beams with five different linear energy transfer (LET) values on adventitious shoots from in vitro leaf explants of Saintpaulia ionahta Mauve cultivar with regard to tissue increase, shoots differentiation and morphology changes in the shoots. Materials and methods: In vitro leaf explant samples were irradiated with carbon ion beams with LET values in the range of 31∼151 keV/µm or 8 MeV of X-rays (LET = 0.2 keV/µm) at different doses. Fresh weight increase, surviving fraction and percentage of the explants with regenerated malformed shoots in all the irradiated leaf explants were statistically analysed. Results: The fresh weight increase (FWI) and surviving fraction (SF) decreased dramatically with increasing LET at the same doses. In addition, malformed shoots, including curliness, carnification, nicks and chlorophyll deficiency, occurred in both carbon ion beam and X-ray irradiations. The induction frequency with the former, however, was far more than that with the X-rays. Conclusions: This work demonstrated the LET dependence of the relative biological effectiveness (RBE) of tissue culture of Saintpaulia ionahta according to 50% FWI and 50% SF. After irradiating leaf explants with 5 Gy of a 221 MeV carbon ion beam having a LET value of 96 keV/µm throughout the sample, a chlorophyll-deficient (CD) mutant, which could transmit the character of chlorophyll deficiency to its progeny through three continuous tissue culture cycles, and plantlets with other malformations were obtained.

Reference gene selection for quantitative real-time PCR normalization in Reaumuria soongorica.

Despite its superiority for evaluating gene expression, real-time quantitative polymerase chain reaction (qPCR) results can be significantly biased by the use of inappropriate reference genes under different experimental conditions. Reaumuria soongorica is a dominant species of desert ecosystems in arid central Asia. Given the increasing interest in ecological engineering and potential genetic resources for arid agronomy, it is important to analyze gene function. However, systematic evaluation of stable reference genes should be performed prior to such analyses. In this study, the stabilities of 10 candidate reference genes were analyzed under 4 kinds of abiotic stresses (drought, salt, dark, and heat) within 4 accessions (HG010, HG020, XGG030, and XGG040) from 2 different habitats using 3 algorithms (geNorm, NormFinder, and BestKeeper). After validation of the ribulose-1,5-bisphosphate carboxylase/oxygenase large unite (rbcL) expression pattern, our data suggested that histone H2A (H2A) and eukaryotic initiation factor 4A-2 (EIF4A2) were the most stable reference genes, cyclophilin (CYCL) was moderate, and elongation factor 1α (EF1α) was the worst choice. This first systematic analysis for stably expressed genes will facilitate future functional analyses and deep mining of genetic resources in R. soongorica and other species of the Reaumuria genus.

The Solanum lycopersicum auxin response factor SlARF2 participates in regulating lateral root formation and flower organ senescence

ARF2 as apleiotropic developmental regulator has been reported in Arabidopsis thaliana and tomato (Solanum lycopersicum). The present study showed SlARF2 transcripts in all tomato plant tissues but with higher accumulation in flowers. During bud-anthesis stages, SlARF2 transcripts showed a dynamic expression pattern in sepal, stamen, ovary and petal. Hormone treatment analysis suggested that SlARF2 transcript accumulation was positively regulated by auxin and gibberellic acid, and negatively regulated by ethylene in tomato seedlings. Phenotypes and molecular analyses of SlARF2-upregulated transgenic tomato indicated that SlARF2 regulated tomato lateral root formation and flower organ senescence may be partially mediated by regulating the gene expression of auxin and ethylene response factors. The data enlarges the functional characterization of SlARF2 in tomato, and broadens our understanding of auxin signaling in regulating plant growth and development.

Molecular mechanisms of foliar water uptake in a desert tree

Foliar water uptake (FWU) plays a significant role in maintaining the stability of fragile ecosystems. However, to date, the molecular mechanism of FWU is not fully understood. Hereby, we thoroughly elucidated the relationship of sap flow velocity and the expression patterns of Aquaporin genes in a desert plant Tamarix ramosissima, and found that only PIP2-1 was up-regulated with increasing relative air humidity at night. This result suggested that the PIP2-1 gene could be in charge of regulating FWU. This is the first time a molecular mechanism for regulating FWU that would allow desert plants to adapt to extreme drought has been documented.

Phenotypic variation of sweet sorghum after carbon ion beam irradiation

The survival rate, DNA mutation rate, phenotype variation, sequence analysis of Hd1 and Hd3a were investigated after the dry seeds of sweet sorghum were irradiated by carbon ions. The results indicate that there was a marked stimulatory effect under low doses in terms of survival rate. The carbon ion irradiation also induced phenotypic variation and the mutation frequency differed as the dose increased. The maximum DNA mutation rate was 18.95%, which occurred at 200 Gy, whereas the mutation rate decreased to 17.87% at 240 Gy. The sequence analysis indicated that there was no difference between KF and KC for the Hd1 gene, but 2bp insertions were clearly observed in KF compared to KC in the case of the Hd3a gene. In conclusion, there was a significant phenotypic variation after carbon ion beam irradiation in sweet sorghum.

Brief Overview of Sweet Sorghum Irradiated by Carbon Ion Beam

Sweet sorghum [Sorghum bicolor (L.) Moench] is a C4 plant characterized by a high photosynthetic efficiency and a high biomass- and sugar- yielding crop. However, the current varieties of sweet sorghum cannot meet the rapid growth demand for bio-ethanol production because of its low sugar content in China. To breed novel varieties to provide excellent raw materials for bio-ethanol production, the dry seeds were irradiated by carbon ion beam irradiation with different doses in sweet sorghum, resulting in acquiring an early-maturity mutant at 80 Gy dose, which the growth period was stably shortened for around 20 days compared to wild-type plant. In this paper, we briefly summarized the biological effects induced by carbon ion beam, the characters of early-maturity mutant, and revealed corresponding mechanisms from the point of view of morphological, physiological and molecular levels. In conclusion, there were significant effects on sweet sorghum irradiated by carbon ion beam.