香蕉為典型的更年性果實，後熟過程中的生理生化反應，會影響果實品質及貯運。運用RNA干擾技術 (RNA interference, RNAi)，分別抑制香蕉乙烯生合成關鍵酵素ACC氧化酶Mh-ACO1及Mh-ACO2基因表現，二種RNAi轉殖香蕉的乙烯生成皆受到抑制，進而延緩果實後熟。進一步進行RNAi轉殖香蕉的轉錄體 (transcriptome) 分析，結果顯示香蕉乙烯生合成相關基因之表現會影響澱粉/蔗糖代謝及糖解途徑相關基因之表現。RNAi轉殖香蕉中，蔗糖合成相關基因下調、蔗糖分解相關基因上調，顯示抑制乙烯生成會造成蔗糖累積量下降。本研究之成果可作為調控香蕉採後生理之重要參考，已刊登於Plants期刊 (Plants 2020, 9, 1120; doi:10.3390/plants9091120)。
基因表現熱圖 (heat map) 顯示RNAi轉殖香蕉中蔗糖代謝相關基因之表現情形
運用即時定量反轉錄聚合酶連鎖反應 (real-time quantitative reverse transcription polymerase chain reaction, real-time qRT-PCR) 確認各後熟階段之轉殖香蕉中的基因表現。
The banana is a typical climacteric fruit that undergoes ethylene dependent ripening. During fruit ripening, ethylene production triggers a developmental cascade that results in a series of physiological and biochemical changes. The fruit transcriptomes of untransformated wild-type (WT) and RNAi transgenic banana plants for Mh-ACO1 and Mh-ACO2 have been previously sequenced and analyzed, and most of the differentially expressed genes were enriched in ‘carbon fixation in photosynthetic organism’, ‘cysteine and methionine metabolism’, ‘citrate cycle (tricarboxylic acid cycle, TCA cycle)’, and ‘starch and sucrose metabolism’ based on Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation. In this research, we investigated the expression fluctuations of genes involved in carbohydrate metabolism affected by alterations of ethylene biosynthesis associated with ripening in banana fruits. Expression profiles of sucrose synthase, sucrose phosphate synthase, neutral invertase, and acidic invertase/β-fructofuranosidase, as analyzed by Avadis and Trinity, showed that both analyses were complementary and consistent. The overall gene expression tendency was confirmed by the implementation of quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) with mRNAs of banana fruits in Mh-ACO1 and Mh-ACO2 RNAi transgenic plants. These results indicated that altered expression of genes associated with ethylene biosynthesis strongly influenced the expression levels of genes related to starch and sucrose metabolism, as well as the glycolysis pathway in ripening banana fruits.
Xia Y, Chiu C-H, Do Y-Y, Huang P-L (2020) Expression fluctuations of genes involved in carbohydrate metabolism affected by alterations of ethylene biosynthesis associated with ripening in banana fruit. Plants 9:1120. (doi:10.3390/plants9091120)