RESUMO
We isolated a full-length cDNA (PeERS2) that encoded the homologue in passion fruit of ERS1 of Arabidopsis and examined its expression during development of passion fruit. PeERS2 was 2357 bp long and included a single open reading frame that encoded a putative protein of 634 amino acids with a calculated molecular mass of 70.8 kDa. Expression of PeERS2 mRNA in arils of passion fruit was enhanced during ripening and after treatment with ethylene, but its level remained very low in seeds over the course of ripening. Accumulation of PeERS2 mRNA in arils was markedly reduced in fruits treated with 2,5-norbornadiene (NBD), but simultaneous application of ethylene abolished the inhibitory effects of NBD, suggesting that the continuous action of ethylene might promote ripening, with a concomitant increase in the abundance of PeERS2 mRNA. Levels of transcripts of the PeERS1 and PeERS2, which encode similar but not identical receptors for ethylene, increased during senescence of flowers and expression of PeERS2 mRNA was also enhanced during formation of the separation layer. The levels of transcripts of PeETR1 (the gene for yet another ethylene receptor) and PeERS1 were, respectively, higher than those of PeERS2 in sepals and ovaries. The transcripts of all three genes for ethylene receptors were barely detectable in anthers. These results suggest that the expression of the three genes for ethylene receptors is differentially regulated and that expression of the gene for PeERS2 is regulated not only by ethylene itself but also by developmental factors. Expression of each of the three individual genes for ethylene receptors might be controlled by different molecular mechanisms in the various tissues.
