Stage- and Tissue-Specific Expression of Ethylene Receptor Homolog Genes during Fruit Development in Muskmelon1

Abstract

We isolated two muskmelon (Cucumis melo) cDNA homologs of the Arabidopsis ethylene receptor genes ETR1 and ERS1 and designated them Cm-ETR1 (C. melo ETR1; accession no. AF054806) and Cm-ERS1 (C. melo ERS1; accession no. AF037368), respectively. Northern analysis revealed that the level of Cm-ERS1 mRNA in the pericarp increased in parallel with the increase in fruit size and then markedly decreased at the end of enlargement. In fully enlarged fruit 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 indicate 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 distinct roles in particular fruit tissues at particular developmental stages.

Ethylene receptors and genetic engineering of ethylene sensitivity in plants.

“…3, the level of Cm-ERSI mRNA in flesh dynamically increased during fruit enlargement, and decreased at the end of enlargement (Sato-Nara et al 1999a). Such an increase of mRNA for tomato ethylene receptor genes is not observed in early-developing fruit (Lashbrook et al 1998).…”

“…ETR1 homologs have also been isolated from other plants: the NR gene (Wilkinson et al, 1995), LeETRI and LeETR2 cDNAs (Lashbrook et al, 1998), LeETR4 and LeETR5 cDNAs (Tieman and Klee,1999) from Lycopersicon esculentum, the RPERSl eDNA from Rumex palustris (Vriezen et al, 1997), Cm -ETRI and Cm -ERSI cDNAs from Cucumis meld (Sato -Nara et al, 1997, 1999a) and the PE -ETRI and PE -ERSI cDNAs from Passiflora edulis (Mita et al, 1998). In addition, the sequences of putative ethylene receptor genes and cDNAs from several plants have been registered in databanks and the plant gene register of Plant Physiology (Table 1).…”

“…Five ethylene receptor genes were expressed ubiquitously in Arabidopsis plants, but each gene was strongly expressed in its particular tissues and stages (Hua and Meyerowit, 1998, Table 1). Five genes in tomato and two genes in melon were also differentially regulated throughout plant development (Lashbrook et al, 1998, Klee et al 1998, Sato -Nara et al 1999a, Tieman and Klee, 1999. Regulation of each ethylene receptor gene by ethylene is different among distinct members in the same species (e.g.…”

“…3;Lashbrook et al, 1998;Sato-Nara et al, 1999a). LeETR1 is expressed constitutively in all plant tissues, and LeETR2 is expressed at low levels throughout the plant except for high levels in imbibing tomato seeds prior to germination (Lashbrook et al,1998).…”

“…The ETR1 gene, which encodes an ethylene receptor, has been isolated and characterized (Chang et al,1993), and other ETR1-like genes (Hua et al,1995(Hua et al, ,1998Hua and Meyerowitz,1998;Sakai et al, 1998) have also been identified in Arabidopsis. Based on sequence similarity and structural features of the proteins, ETR1-like genes have been isolated from several other plants including tomato (Wilkinson et al, 1995, Lashbrook et al, 1998, Tieman and Klee, 1999, Rumex palustris (Vriezen et al, 1997) and melon (Sato-Nara, et al, 1997, 1999a. Using similar molecular genetic approach, genes related to the ethylene signaling pathway have also been isolated and characterized (Guzman and Ecker, 1990;Kieber et a!.,1993;Roman et al, 1995;Chao et al, 1997;Alonso et al, 1999).…”