Molecular Cloning and Characterization of Fruit Softening Related Gene β-Mannanase from Banana Fruit

A 1 250 bp cDNA fragment encoding β-mannanase, named MaMAN, was cloned from banana （Musa spp cv. Baxi） fruit using degenerate primers designed with reference to the conserved nucleic acid sequences of known β-mannanase genes by RT-PCR. Sequence analysis showed that MaMAN cDNA encompassed a 1 085 bp open-reading frame （ORF）, encoding a predicted polypeptide of 395 amino acids. Alignment of the deduced amino acid sequence of MaMAN and other putative β-mannanases showed that MaMAN has an identity of 86, 70, 69, 54, and 57%, respectively, to β-mannanases from tomato, lettuce, arabidopsis, carrot and oryza sativa. The catalytic residues： Asn203, Glu204, Glu318 and the active site residues： Arg86, His277, Tyr279, and Trp360, which were strictly conserved in the glycoside hydrolase family 5 to which all β-mannanases belonged, were found in MaMAN. Semi-quantitative RT-PCR revealed that the level of MaMAN transcript in the pulp increased during banana fruit ripening, suggesting that MaMAN was likely to be involved highly in banana fruit softening.

In Silico Cloning and Sequence Analysis of Phospholipase Dα Gene from Peach Fruit

Phospholipase D （PLD, EC 3.1.4.4） plays an important role in adaptive response of postharvest fruit to environment. In this study, a novel cDNA of PLDα was isolated with the strategy of in silico cloning in combination with RT-PCR from peach （Prunus persica L. cv. Jiubao）. The obtained PLDα gene contained a complete open reading frame encoding a 92- kDa protein of 810 amino acid residues, which possessed the characteristic C2 domain and two catalytic HKD motifs. The alignment analysis of the deduced peach PLDa protein with other known PLDα family proteins indicated that peach PLDα was conserved and highly homologous with strawberry PLDα. Semi-quantitative RT-PCR and Northern blot analysis indicated PLDα mRNA in peach fruits could be induced by low temperature. This work provided a scientific basis for further investigating the mechanism of postharvest fruit adaptation to low temperature.

Pre-harvest and post-harvest application of benzothiadiazole for controlling anthracnose and extending shelf life of harvested banana

Anthracnose,caused by the fungus Colletotrichum musae,is a serious latent post-harvest disease of banana,which results in major economic losses during transportation and storage.Benzo-thiadiazole-7-carbothioic acid S-methyl ester(BTH),a functional analogue of the plant endogenous hormone-like compound salicylic acid(SA),has been known to possess resistant effects on some diseases caused by fungi.The aim of present study was to select an appropriate BTH concentration and an appropriate stage of banana ripening for its application in controlling anthracnose and extending shelf life of harvested banana fruit.Different concentrations of BTH(50,100,200 and 300μg/mL)were applied at different stages of banana fruit ripening,including one week,two weeks and one month before harvest.The results suggest that while the concentrations of BTH ranging from 50μg/mL to 200μg/mL in both pre-harvest and post-harvest application,this could control anthracnose of harvested banana fruit,the appropriate concentration of BTH in both pre-harvest and post-harvest treatment was 100μg/mL and the best time of BTH treatment was two weeks before harvest.Examination of quality parameters including peel color and firmness indicated that 100μg/mL BTH treatment delayed banana fruit ripening at room temperature.