臺灣博碩士論文加值系統

摘要 對於植
物細胞而言，細胞與細胞間的溝通對其生長及發育是相當重要的。 有越來越多的證
據顯示，面對外界環境改變所產生的刺激以及本身各個生 長發育階段的變化，生物
體可藉由一個位在細胞表面的受體接收訊息，再 利用蛋白質磷酸化及去磷酸化的機
制，經由一連串的訊息傳導網路，影響 各種生理生化反應。其中，蛋白激正是催
化蛋白質磷酸化反應之關鍵酵 素。香蕉為典型更年性果實，乙烯深切地影響其後熟
生理，而近年來的研 究更顯示，乙烯訊息的接收與傳導也是經由蛋白質磷酸化及去
磷酸化反應 的調控，因此在果實後熟過程中，必定也有一群蛋白激參與訊息傳導
的 重要工作。
我們自香蕉後熟相關之蛋白激cDNA選殖系中，選取編號為pBPK10之cDNA 選殖系進
行核酸定序分析，得其全長為1758 bp，解碼529個胺基酸，推演 之分子量為57709D
a，pI值為6.21。若將推演所得之胺基酸序列與已發表 之基因序列以電腦比對，此
基因與植物中一類Leucine rich receptor-like protein kinases基因之蛋白激催
化組區具有很高之相似性（77－85%）。 由北方雜交分析（Northern analysis）之結
果顯示，BPK10基因於後熟香蕉 果實中表現之產物大小約為4.25kb，其mRNA之累積量
在果肉中會隨香蕉成熟 度之增加而增加，在果皮中則呈現先上升而後下降之趨勢。而
且此基因之 mRNA大量表現於後熟果實中，雌蕊及苞片次之，在子房及懸浮細胞與癒
合組 織中也有少量之表現，顯示此一基因確實與香蕉之後熟有關。
由基因組南方氏雜交分析（genomic Southern analysis）結果可知香蕉蛋白 激基因
BPK10可能屬於低拷貝數的基因。為進一步瞭解其基因之結構特性及 可能扮演之生理角
色，本實驗室以pBPK10 cDNA為探針，進行基因組庫 （genomic library）篩選
，得到18個基因組選殖系（genomic clones）並加 以分析歸類，之後我們選取其中一
個基因組選殖系(BPSK44，進行限制圖譜 及核酸定序分析。目前定序工作正進行中，
待定序工作完成後將分析其基因 結構特性及功能。

Abstract

Intercellular communication is fundamental to the growth and development
of higher plants. A growing body of evidence suggests that responses to ma
ny signals such as plant hormones and foreign and endogenous carbohydrat
e elicitors are mediated by cell-surface receptors and may involve ki
nase -mediated phosphorylation. Protein phosphorylation is now recogni
zed as the major general mechanism by which intracellular events are c
ontrolled by external physiological stimuli. There is an integrated net
work of regulatory pathways, mediated by phosphorylation-dephosphor
ylation, that allows diverse cellular events to be coordinated by
neural and hormonal stimuli. Bananas are typical climacteric fruit
s and their ripening are regulated by ethylene. Evidence has been
presented that the ethylene signal is transduced via protein phosp
horylation events in plant cells. To identify protein kinases which
are involved in banana fruit ripening, we isolated several ripening-re
lated cDNAs encoding protein kinases in banana. A cDNA clone, pBPK10, codi
ng for protein kinase was isolated from a banana fruit cDNA library.
The cDNA clone pBPK10 is 1758 bp. long and encodes a polypeptide of 529 ami
no acids with a predicted isoelectric point of 6.21 whose molecul
ar mass is 57709 Da. The deduced amino acid sequence from cDNA pBPK10
has a putative transmembrane domain and the potential cytoplasmic domai
n is highly similar to leucine rich receptor-like protein serine / th
reonine kinase in plants. Northern analysis showed that the abundance of BP
K10 transcript was largest in mature banana fruit. Its expression increas
ed with the ripening degree in pulp, whereas, the gene expression was mor
e profoundly at stage 3 in peel. The differential expression of BPK10 in pe
el and pulp suggests that the gene may have different functions in
peel and pulp. Genomic Southern analysis indicated that BPK10 belongs to
small multigene family. Taken the structural features and the expression
pattern together, we suggest that BPK10 may play important role in
fruit ripening.