Abstract
The gaseous plant hormone ethylene regulates many aspects of plant growth, development and responses to the environment. Constitutive triple response 1 (CTR1) is a central regulator involved in the ethylene signal transduction pathway. To obtain a better understanding of this particular pathway in cucumber, the cDNA-encoding CTR1 (designated CsCTR1) was isolated from cucumber. A sequence alignment and phylogenetic analyses revealed that CsCTR1 has a high degree of homology with other plant CTR1 proteins. The ectopic expression of CsCTR1 in the Arabidopsis ctr1-1 mutant attenuates constitutive ethylene signaling of this mutant, suggesting that CsCTR1 indeed performs its function as negative regulator of the ethylene signaling pathway. CsCTR1 is constitutively expressed in all of the examined cucumber organs, including roots, stems, leaves, shoot apices, mature male and female flowers, as well as young fruits. CsCTR1 expression gradually declined during male flower development and increased during female flower development. Additionally, our results indicate that CsCTR1 can be induced in the roots, leaves and shoot apices by external ethylene. In conclusion, this study provides a basis for further studies on the role of CTR1 in the biological processes of cucumber and on the molecular mechanism of the cucumber ethylene signaling pathway.
Highlights
Ethylene (C2H4) was the first example of a gaseous signaling molecule involved in biological systems and was discovered more than a century ago
A sequence analysis showed that the open reading frame (ORF) of CsCTR1 was 2559 bp in length, encoding a putative polypeptide of 852 amino acids with a molecular mass of 94.521 kDa and isoelectric point of 5.77
Sequence that was obtained from the cucumber genome database contained 15 exons and 14 introns, similar to the Arabidopsis Constitutive triple response 1 (CTR1) (AtCTR1), and the position and size of the exons in CsCTR1 exhibited a high degree of similarity with those in AtCTR1 (Figure 1)
Summary
Ethylene (C2H4) was the first example of a gaseous signaling molecule involved in biological systems and was discovered more than a century ago. Components of the ethylene signal transduction pathway were identified using Arabidopsis mutants that were altered in the seedling triple response [2], and a basic model of the ethylene signal transduction pathway has been established [3]. Similar to the bacterial two-component histidine kinase sensors [4,5,6]. These receptors are localised in the Endoplasmic reticulum (ER) membrane and Golgi apparatus [7]. Studies have found that all of these genes have redundant functions as negative regulators of ethylene signaling, and their double, triple and quadruple mutants result in constitutive responses to ethylene [5,8]
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