Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2002
Publication Date: 11/1/2002
Citation: LECLERCQ, J., ADAMS-PHILLIPS, L., ZEGZOUTI, H., JONES, B., LATCHE, A., GIOVANNONI, J.J., PECHE, J., BOUZAYEN, M. LECTR1, A TOMATO CTR1-LIKE GENE, DEMONSTRATES ETHYLENE SIGNALING ABILITY IN ARABIDOPSIS AND NOVEL EXPRESSION PATTERNS IN TOMATO. PLANT PHYSIOLOGY. 2002. V. 13. P. 1132-1142. Interpretive Summary: The plant hormone ethylene is involved in a variety of developmental and physiological processes in plants, including senescence and fruit ripening. It also plays an important role in physiological responses to environmental stresses such as water deficit, mechanical wounding and pathogen attack. The unraveling of the molecular basis of the ethylene perception and signal transduction pathway has been enhanced by the use of Arabidopsis thaliana mutants altered in the seedling triple response. The triple-response is exhibited by seedlings treated with ethylene and results in: (i) inhibition of root elongation, (ii) shortening and radial swelling of the hypocotyl and, (iii) exaggerated curvature of the apical hook. Numerous loci have been identified and many corresponding genes cloned, representing various steps in ethylene signaling from receptors through transcription factors. LeCTR1 was initially isolated by both DDRT-PCR screening for tomato (Lycopersicon esculentum) fruit ethylene-inducible genes and through homology with the Arabidopsis thaliana CTR1 cDNA. Here we show LeCTR1 encodes a functional ethylene signal transduction component induced during fruit ripening.
Technical Abstract: LeCTR1 shares strong nucleotide sequence homology with Arabidopsis CTR1, a gene acting downstream of the ethylene receptor and showing similarity to the Raf family of serine/threonine protein kinases. The length of the LeCTR1 transcribed region from ATG to stop codon (12000 bp) is more than twice that of Arabidopsis CTR1 (4700 bp). Structural analysis reveals perfect conservation of both the number and position of introns and exons in LeCTR1 and Arabidopsis CTR1. The introns in LeCTR1 are much longer, however. To address whether this structural conservation is indicative of functional conservation of the corresponding proteins, we expressed LeCTR1 in the Arabidopsis constitutive ethylene response 1 (ctr1-1) mutant under the direction of the 35S promoter. Our data clearly show that ectopic expression of LeCTR1 in the Arabidopsis ctr1-1 mutant can restore normal ethylene signaling. The recovery of normal ethylene sensitivity upon heterologous expression of LeCTR1 was also confirmed by restored glucose sensitivity absent in the Arabidopsis ctr1-1 mutant. Expression studies confirm ethylene responsiveness of LeCTR1 in various tissues including ripening fruit and may suggest the evolution of alternate regulatory mechanisms in tomato versus Arabidopsis.