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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.
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