The Analysis Of Structure MuArf1, A Member Of Small GTPase Gene Family, And Its Expression During Postharvest Ripening In Banana Fruit

As important switches in cell signaling, the small GTPases are apparently conserved in all organisms. In spite of their small size, the interaction of small GTPase with various regulators and effectors generates functional diversity and creates novel functions in different phyla. Functional innovation of a conserved GTPase together with birth of new members of the superfamily endows plants with the capacity to use small GTPase as a key molecular switch for the modulation of many plant-specific signaling pathways and functions. It is one of the hot topics of developmental biology. The function of plant Ran family, however, has not been elucidated, although the research progresses of its interactional proteins are intriguing.MuArf1 is the coding gene of Arf homologous protein. Its full length cDNA is 546bp, the protein encoded was composed by 181 amino acids, And the full length DNA is 1998bp included 5 exons and 4 introns. One of the introns included an integrated ORF, from which it is speculated that introns may affect genic expression and regulation. But the function of MuArf1 gene in fruit ripening has not been reported. In the research, MuArf1 was found to have the role in fruit ripening at mRNA difference expression level, suggesting that it may be a important factor in signal transduction and act in many cellular basic physiological processes.By the system analysis of transient expression in onion coat, MuArf1 protein was mainly localized at cell membrane and cytoplasm, which was consistent with Arf localization in Arabidopsis, revealing the MuArf1 role for cell-membrane-cytoplasm transportion. MuArf1 gene transcripts was constitutive expression in banana tissue., which was more in reproductive and eugenic organs such as fruit harvested at 0 day, and less in old leaves. For analyzing MuArf1 expression in different ripening of fruit and the relation with ethylene signal, according to ethylene change tendency, select the fruit harvested in different ripening as materials of expression analysis, extracted RNA and reverse transcripted into cDNA as template. By RT-PCR semi-quantity, it was found that MuArf1 expression had difference in the different-ripening fruit. The change trend was descending and then ascending. In normal ripening fruit, there was a peak of expression at 12 day after fruit was harvested, which was 2 day earlier than the peak time of relevant endogenesis ethylene. Compared with normal ripening fruit, the treatment of exogenous ethylene promoted the expression; and the peak from the fruit induced by ethylene emerged 2 day after fruit was harvested, earlier 6 day than normal and higher peak. Ethylene absorbent basicly inhibited MuArf1 expression and postponed peak, and the whole trend showed slow ascending. Therefore, it was speculated that MuArf1 acted significantly in ethylene signal transduction, and may relate with fruit early development and ripeness in fruit late development.It is the first expression analysis to MuArf1 gene cloned from banana, which has important meaning on theory and instruction, and needs a further study.