Zhu Ben-zhong

Cloning and DNA-binding properties of ethylene response factor, LeERF1 and LeERF2, in tomato.

Two new genes, LeERF1 andLeERF2, were isolated from a tomato (Lycopersicon esculentum cv. Lichun) cDNA library. Phylogenetic analysis indicated that they encoded Ethylene Responsive Element Binding Proteins (EREBPs), characterized by a conserved ERF (ethylene response factor) domain of specific binding plant cis-acting elements GCC box. Both LeERF1 and LeERF2 proteins were obtained via prokaryotic expression and purification. Electrophoretic mobility shift assay showed that LeERF1 and LeERF2 protein could bind to the promoter of the NP24 gene coding for pathogenesis-related protein osmotin precursor but not the mutant promoter where its GCC box was deleted. Polyclonal antibodies of LeERF1 and LeERF2 blocked their binding in vitro.

Relationship between calcium and ABA in ethylene synthesis in tomato fruit

The influence of calcium and ABA on ethylene biosynthesis was investigated at different stages and patterns of tomato ( Lycopersicon esculentum cv. Lichun) fruit to analyse the relationship between calcium and ABA in relation to the ethylene biosynthesis system. The ethylene production of discs excised from mature green tomato fruits increased rapidly with 100 μmol/l ABA or 100 mmol/l calcium treatment. The increase with the two treatments combined was more than that after application of a single chemical, which suggests that these two chemicals could play synergistic roles in the ethylene synthesis of mature green tomato fruits. It was also found that application of the calcium chelator EGTA inhibited ethylene synthesis, and the production of ethylene after application of EGTA plus ABA was higher than that after treatment with EGTA alone. However, the effect changed when immature fruits were treated with these chemicals. ABA inhibited ethylene synthesis obviously and calcium still promoted it. When we treated immature fruit discs with both calcium and ABA simultaneously, ethylene production was more than that of ABA and less than that of calcium, which indicates that ABA and calcium play agonistic roles in ethylene biosynthesis of the immature tomato fruit discs. Furthermore, ethylene release from transgenic antisense ACS immature tomato fruit discs with application of both calcium and ABA was inhibited markedly, but was stimulated when the mature fruits were treated with ABA and calcium. All of these data suggest that there are different relationships between calcium and ABA in the ethylene synthesis system in different patterns and stages of tomato fruit ripening.

Influence of salt stress on expression of some genes involved in the ethylene signalling pathway in tomato seedlings

Differences in immunostimulation activity of CpG oligodeoxynucleotides (ODNs) between pigs and mice were studied. In accordance with current research data, three kinds of CpG ODN – 2006, D19 and 1826, which were identified as optimally active in humans, pigs and mice, respectively – and control ODN D48, a non CpG-containing ODN, were selected and synthesized. Results indicated that CpG ODN D19 strongly stimulated the proliferation of porcine peripheral blood mononuclear cells (PBMCs), and the amount of γ-interferon in the supernatant of activated cells increased, exceeding that of all other ODNs tested, while mouse splenocytes did not respond. CpG ODN 1826 strongly stimulated the proliferation of mouse splenocytes, but porcine PBMCs remained unresponsive. CpG ODN 2006 effectively stimulated proliferation of both porcine PBMCs and mouse splenocytes. Therefore some specific CpG ODNs, D19 and 1826, selectively stimulated animal species, while CpG ODN 2006 possessed a common stimulation effect. In addition, CpG ODN D19 predominantly induced the response of type 1 T-helper cells in vivo .