Effect of pollination and exogenous ethylene on accumulation of ETR1 homologue transcripts during flower petal abscission in geranium (Pelargonium x hortorum L.H. Bailey).

We have isolated two cDNAs from geranium, PhETR1 and PhETR2. The deduced amino acid sequences of PhETR1 anti PhETR2 share 78% and 79% identity with ETR1 from Arabidopsis thaliana respectively. These genes are members of a multigene family and are expressed at moderate levels in leaves, pedicels, sepals, pistils and petals, and at very low levels in roots. PhETR1 and PhETR2 mRNAs are expressed in geranium florets long before they are receptive to pollination and transcript levels remain constant throughout floral development. Message levels of PhETR1 and PhETR2 in pistils and receptacles are unaffected by self-pollination or treatment with 1 micro/l ethylene that induces petal abscission. Our results indicate that the amount of PhETR1 and PHETR2 mRNA is not indicative of the level of sensitivity of geranium florets to ethylene.