Peach (Prunus persica) fruit emit more than 100 volatile organic compounds. Among these volatiles, γ-decalactone is the key compound that contributes to peach aroma. The final step in lactones biosynthesis is catalyzed by alcohol acyltransferases (AATs). In this study, five AAT genes were isolated in the peach genome, and the ways that these genes contribute toward the peach aroma were studied. The sequence analysis of the five AATs showed PpAAT4 and PpAAT5 are truncated genes, missing important residues such as HXXXD. The expressions of PpAATs were investigated to identify the roles in creating the peach aroma. The results indicated that only PpAAT1 is highly expressed during γ-decalactone formation. A functional survey of the five PpAATs, using the oleaginous yeast expression system, suggested that only PpAAT1 significantly increased the γ-decalactone content, whereas the other four PpAATs did not significantly alter the γ-decalactone content. Enzyme assays on PpAATs heterologously expressed and purified from Escherichia coli indicated that only PpAAT1 could catalyze the formation of γ-decalactone. All results indicated that PpAAT1 is a more efficient enzyme than the other four PpAATs during the γ-decalactone biosynthesis process in peach fruit. The results from this study should help improve peach fruit aroma.
Bin Peng, Jianlan Xu, Zhixiang Cai, Binbin Zhang, Mingliang Yu, and Ruijuan Ma
Cai-Hong Jia, Ju-Hua Liu, Zhi-Qiang Jin, Qiu-Ju Deng, Jian-Bin Zhang, and Bi-Yu Xu
A full-length cDNA isolated from banana (Musa acuminata L. AAA group) fruit was named MaMDH, containing an open reading frame encoding 332 amino acids that represents the gene for cytoplasmic malic dehydrogenase (MDH). Sequence analysis showed that MaMDH shares high similarity with MDHs from castor bean (XP_002533463), tobacco (CAC12826), peach (AAL11502), and chickpeas (CAC10208). Real-time quantitative polymerase chain reaction (PCR) analysis of MaMDH spatial expression showed that it was expressed in all organs examined: roots, rhizomes, leaves, flowers, and fruits. The expression was the highest in flowers followed by the fruits and roots, whereas the rhizomes and leaves displayed the lowest expression levels. Real-time quantitative PCR revealed that MaMDH exhibited differential expression patterns in post-harvest banana fruits correlating with ethylene biosynthesis. In naturally ripened banana fruits, MaMDH expression was in accordance with ethylene biosynthesis. In accordance, for banana fruits treated with the ethylene analog 1-methylclopropene (1-MCP), MaMDH expression levels were inhibited and remained constant. After treatment with ethylene, MaMDH expression in banana fruits significantly increased with ethylene biosynthesis and peaked 3 days after harvest, which was 11 days earlier than that in naturally ripened banana fruits. These results suggest that MaMDH expression is induced by ethylene to regulate post-harvest banana fruits ripening.
Bin Cai, Cheng-Hui Li, Ai-Sheng Xiong, Ri-He Peng, Jun Zhou, Feng Gao, Zhen Zhang, and Quan-Hong Yao
The database of grape transcription factors (DGTF) is a plant transcription factor (TF) database comprehensively collecting and annotating grape (Vitis L.) TF. The DGTF contains 1423 putative grape TF in 57 families. These TF were identified from the predicted wine grape (Vitis vinifera L.) proteins from the grape genome sequencing project by means of a domain search. The DGTF provides detailed annotations for individual members of each TF family, including sequence feature, domain architecture, expression information, and orthologs in other plants. Cross-links to other public databases make its annotations more extensive. In addition, some other transcriptional regulators were also included in the DGTF. It contains 202 transcriptional regulators in 10 families.
Wei Hu, Ju-Hua Liu, Xiao-Ying Yang, Jian-Bin Zhang, Cai-Hong Jia, Mei-Ying Li, Bi-Yu Xu, and Zhi-Qiang Jin
The banana, a typical climacteric fruit, undergoes a postharvest ripening process followed by a burst in ethylene production that signals the beginning of the climacteric period. Postharvest ripening plays an important role in improving the quality of the fruit as well as limiting its shelf life. To investigate the role of glutamate decarboxylase (GAD) in climacteric ethylene biosynthesis and fruit ripening in postharvest banana, a GAD gene was isolated from banana, designated MuGAD. Coincidently with climacteric ethylene production, MuGAD expression as well as the expression of the genes encoding the Musa 1-aminocyclopropane-1-carboxylate synthase (MaACS1) and Musa 1-aminocyclopropane-1-carboxylate oxidase (MaACO1) greatly increased during natural ripening and in ethylene-treated banana. Moreover, ethylene biosynthesis, ripening progress, and MuGAD, MaACS1, and MaACO1 expression were enhanced by exogenous ethylene application and inhibited by 1-methylcyclopropene (1-MCP). Taken together, our results suggested that MuGAD is involved in the fruit ripening process in postharvest banana.