Forty-five bacterial isolates were collected from surface-sterilized leaves of mulberry (Morus alba L.). By screening their antagonistic activities a

Mitogen-activated protein kinase kinase kinase (MAPKKK, MAP3K) is located upstream of the mitogen-activated protein kinase (MAPK) cascade pathway and is responsible for receiving and transmitting external signals to the downstream MAPKKs. Although a large number of MAP3K genes play important roles in plant growth and development, and response to abiotic and biotic stresses, only a few members’ functions and cascade signaling pathways have been clarified, and the downstream MAPKKs and MAPKs of most MAP3Ks are still unknown. As more and more signaling pathways are discovered, the function and regulatory mechanism of MAP3K genes will become clearer. In this paper, the MAP3K genes in plants were classified and the members and basic characteristics of each subfamily of MAP3K were briefly described. Moreover, the roles of plant MAP3Ks in regulating plant growth and development and stress (abiotic and biotic) responses are described in detail. In addition, the roles of MAP3Ks involved in plant hormones signal transduction pathway were briefly introduced, and the future research focus was prospected.

Anthracnose, caused by Colletotrichum dematium, is a serious threat to the production and quality of mulberry leaves in susceptible varieties. Control of the disease has been a major problem in mulberry cultivation. Some strains of Burkholderia cepacia were reported to be useful antagonists of plant pests and could increase the yields of several crop plants. Although B. cepacia Lu10-1 is an endophytic bacterium obtained from mulberry leaves, it has not been deployed to control C. dematium infection in mulberry nor its colonization patterns in mulberry have been studied using GFP reporter or other reporters. The present study sought to evaluate the antifungal and plant-growth-promoting properties of strain Lu10-1, to clarify its specific localization within a mulberry plant, and to better understand its potential as a biocontrol and growth-promoting agent.

Gamma-aminobutyric acid (GABA) has been reported to accumulate in plants when subjected to salt stress, and GABA-transaminase (GABA-T) is the main GABA-degrading enzyme in the GABA shunt pathway. So far, the salt tolerance mechanism of the GABA-T gene behind the GABA metabolism remains unclear. In this study, the cDNA (designated MuGABA-T) of GABA-T gene was cloned from mulberry, and our data showed that MuGABA-T protein shares some conserved characteristics with its homologs from several plant species. MuGABA-T gene was constitutively expressed at different levels in mulberry tissues, and was induced substantially by NaCl, ABA and SA. In addition, our results demonstrated that exogenous application of GABA significantly reduced the salt damage index and increased plant resistance to NaCl stress. We further performed a functional analysis of MuGABA-T gene and demonstrated that the content of GABA was reduced in the transgenic MuGABA-T Arabidopsis plants, which accumulated more ROS and exhibited more sensitivity to salt stress than wild-type plants. However, exogenous application of GABA significantly increased the activities of antioxidant enzymes and alleviated the active oxygen-related injury of the transgenic plants under NaCl stress. Moreover, the MuGABA-T gene was overexpressed in the mulberry hairy roots, and similar results were obtained for sensitivity to salt stress in the transgenic mulberry plants. Our results suggest that the MuGABA-T gene plays a pivotal role in GABA catabolism and is responsible for a decrease in salt tolerance, and it may be involved in the ROS pathway in the response to salt stress. Taken together, the information provided here is helpful for further analysis of the function of GABA-T genes, and may promote mulberry resistance breeding in the future.

In the present study, the cDNA (designated MuPR1) of PR1 gene was obtained from mulberry. Our results showed that MuPR1 shares some conserved characteristics with its homologues from different plant families. MuPR1 was localized exclusively to the extracellular spaces, and the MuPR1 gene was expressed constitutively in all selected mulberry tissues, although its expression levels varied substantially. It was also showed that MuPR1 expression was induced by pathogen, MeJA, SA and GA₃, and transgenic Arabidopsis overexpressing MuPR1 showed enhanced resistance to Botrytis cinerea and Pst. DC3000. Moreover, the peptide derived from MuPR1 protein C-terminus with a PxGNxxxxxPY motif was suggested to play a role in activating plant resistance. Furthermore, the MuPR1 gene may have roles in mediating the rates of oxygen radical formation and detoxification. Therefore, the MuPR1 gene may be a candidate gene for breeding resistant mulberry varieties in the future.