Interactions between sucrose and jasmonate signalling in the response to cold stress.

BACKGROUND: Jasmonates play an important role in plant stress and defence responses and are also involved in the regulation of anthocyanin synthesis in response to sucrose availability. Here we explore the signalling interactions between sucrose and jasmonates in response to cold stress in Arabidopsis. RESULTS: Sucrose and cold treatments increased anthocyanin content additively. Comprehensive profiling of phytohormone contents demonstrated that jasmonates, salicylic acid and abscisic acid contents increased in response to sucrose treatment in plants grown on agar, but remained considerably lower than in plants grown in compost. The gibberellin GA3 accumulated in response to sucrose treatment but only at warm temperature. The role of jasmonate signalling was explored using the jasmonate response mutants jar1-1 and coi1-16. While the jar1-1 mutant lacked jasmonate-isoleucine and jasmonate-leucine, it accumulated 12-oxo-phytodienoic acid at low temperature on agar medium. Altered patterns of abscisic acid accumulation and higher sugar contents were found in the coi1-16 mutant when grown in compost. Both mutants were able to accumulate anthocyanin and to cold acclimate, but the jar-1-1 mutant showed a larger initial drop in whole-rosette photosystem II efficiency upon transfer to low temperature. CONCLUSIONS: Hormone contents are determined by interactions between temperature and sucrose supply. Some of these effects may be caused indirectly through senescence initiation in response to sucrose availability. During cold stress, the adjustments of hormone contents may compensate for impaired jasmonate signalling, enabling cold acclimation and anthocyanin accumulation in Arabidopsis jasmonate response mutants, e.g. through antagonistic interactions between gibberellin and jasmonate signalling.

Isolation and Identification of Ipomoea cairica (L.) Sweet Gene IcSRO1 Encoding a SIMILAR TO RCD-ONE Protein, Which Improves Salt and Drought Tolerance in Transgenic Arabidopsis.

Ipomoea cairica is a tropical plant and a wild relative of the food plant sweet potato (Ipomoea batatas), listed as one of the most invasive alien species in China. Recently, it has been reported that I. cairica had successfully invaded mangrove wetlands, indicating its high salt tolerance. Based on previous genetic studies, I. cairica offers a good model for characterizing stress-resistant genes. It has recently been identified that the SRO proteins (SIMILAR TO RCD-ONE) play important roles in a variety of stress and developmental responses. Radical-Induced Cell Death1 (RCD1) was the first identified plant SRO protein from Arabidopsis thaliana. As a typical SRO protein, IcSRO1 had a highly conservative WWE domain, a conserved PARP fold and protein C in the RST function area. The expression of IcSRO1 was induced by salt, drought, and the plant hormone ABA. The transgenic Arabidopsis overexpressing IcSRO1 showed higher tolerance against salt and drought stress along with lower accumulation of hydrogen peroxide (H2O2) and superoxide (O2-) than the wild type. The IcSRO1 protein was localized in the nucleus after cultivation in the buffer. Our results indicated it could interact with Arabidopsis SALT OVERLY SENSITIVE 1 (AtSOS1), suggesting IcSRO1 may have similar functions. The pleiotropic effect of IcSRO1 on physiological processes contributes to the improvement of plant tolerance against diverse abiotic stresses, and may be associated with the adaptation of I. cairica to those environments with extreme saline and drought conditions. It therefore provides valuable gene resources for crop breeding enhancement.

Field evaluation of effects of transgenic cry1Ab/cry1Ac, cry1C and cry2A rice on Cnaphalocrocis medinalis and its arthropod predators.

The impacts of transgenic Bt rice on target pests and their predators need to be clarified prior to the commercialization of Bt rice. In this study, the percentages of folded leaves of three transgenic Bt rice lines and non-transgenic parental rice line caused by Cnaphalocrocis medinalis were studied over two successive growing seasons. In addition, the population densities, relative abundance and population dynamics of C. medinalis and four species of its natural arthropod predators were investigated at three sites in China. The results showed that rice line significantly affected the percentages of folded leaves and population densities of C. medinalis larvae. Significantly higher percentages of folded leaves were observed on the non-transgenic rice compared with the three transgenic Bt rice on most sampling dates. Significantly higher densities of C. medinalis larvae and higher relative abundance of C. medinalis within phytophages were found on non-transgenic rice compared with three transgenic Bt rice at different sites across the study period. The population dynamics of C. medinalis larvae were significantly affected by rice line, rice line×sampling date, rice line×year, rice line×sampling date×year. However, there was little, if any, significant difference in the relative abundance, population density and population dynamics of the four arthropod predators between the three Bt rice lines and non-transgenic rice. The results of this study indicate that the Bt toxin in transgenic Bt rice can effectively suppress the occurrence of C. medinalis, but has no significant effects on the occurrence of the four predatory arthropod species.