Stage- and tissue-specific expression of ethylene receptor homolog genes during fruit development in muskmelon

We isolated two muskmelon (Cucumis melo) cDNA homologs of the Arabidopsis e thylene receptor genes ETR1 and ERS1 and designated them Cm-ETR1 (C. melo E TR1; accession no. AF054806) and Cm-ETR1 (C. melo ERS1; accession no. AF037 368), respectively. Northern analysis revealed that the level of Cm-ERS1 mR NA in the pericarp increased in parallel with the increase in fruit size an d then markedly decreased at the end of enlargement. In fully enlarged frui t the level of Cm-ERS1 mRNA was low in all tissues, whereas that of Cm-ETR1 mRNA was very high in the seeds and placenta. During ripening Cm-ERS1 mRNA increased slightly in the pericarp of fruit before the marked increase of Cm-ETR1 mRNA paralleled climacteric ethylene production. These results indi cate that both Cm-ETR1 and Cm-ERS1 play specific roles not only in ripening but also in the early development of melon fruit and that they have distin ct roles in particular fruit tissues at particular developmental stages.