Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2004
Publication Date: 6/8/2004
Citation: Adams-Phillips, L., Barry, C., Kannan, P., Lecercq, J., Bouzayen, M., Giovannoni, J.J. 2004. Ctr1-mediated ethylene signal transduction in tomato is encoded by a multigene family whose members display distinct regulatory features. Plant Molecular Biology. 54:387-404. Interpretive Summary: Ethylene plays an important role in plant growth, development, and physiology including the promotion of seed germination, inhibition of stem and root elongation, leaf expansion, flower formation, senescence and fruit ripening. Economically important fruits such as tomato, apple, pear, melon, squash, peach, avocado, and many other so called climacteric fruit show increased synthesis and dependence upon ethylene for induction and completion of fruit ripening. Ethylene has indeed been shown to regulate expression of numerous genes related to ripening. In Arabidopsis, ethylene is perceived by a family of five ethylene receptors (ETR1, ETR2, ERS1, ERS2, EIN4) with similarity to bacterial two-component histidine kinase receptors. Downstream of the receptors is CTR1, which acts as a negative regulator of ethylene responses. Only one gene with CTR1 function has been isolated to date in Arabidopsis and tests for epistasis with available receptor mutants suggest the product of this single gene is involved in signaling from all members of the receptor family. A CTR1-like gene (LeCTR1) was isolated from tomato and shown through complementation of a ctr1 Arabidopsis mutant to function in ethylene signaling. LeCTR1 mRNA is upregulated by ethylene during fruit ripening), and is shown here to comprise part of a multigene family whose members possess CTR1 function and display differential gene expression. In contrast, in Arabidopsis only one CTR1-like gene has been implicated in ethylene signaling and its mRNA is constitutively expressed.
Technical Abstract: We present here the first experimental evidence of a multigene family of CTR1-like genes which are able to participate in ethylene signal transduction. The family is differentially regulated by ethylene and stages of development marked by increased ethylene biosynthesis. The presence of a multigene family of functional CTR1 genes is not limited to tomato and the possibility of CTR1-like gene loss in Arabidopsis was examined. Somewhat paradoxical is the notion that expression of a negative regulator of ethylene response would increase in response to ethylene. This phenomenon may serve as a mechanism to modulate the sensitivity of a tissue to ethylene to provide the range of responses under various conditions/tissues observed for ethylene.