Characterization of circadian‐regulated mRNAs encoding glycine‐rich RNA‐binding proteins in Pelargonium×hortorum

Abstract

Two cDNAs, PhGRP1 and PhGRP2, with high sequence identity to genes encoding glycine‐rich RNA‐binding proteins, have been cloned from Pelargonium×hortorum. PhGRP is represented in the P.×hortorum genome by a single copy. DNA sequence analysis of two independently isolated cDNAs, PhGRP1 and PhGRP2, indicates that PhGRP2 represents a partially spliced version of PhGRP1. The additional intron‐like sequence in PhGRP2 contains a termination codon, which would result in translation of a truncated protein. Expression of PhGRP1 was high in petals, pistils, roots and stems, and lower in leaves. PhGRP2 transcripts were less abundant than those of PhGRP1 in all tissues, but were proportionately higher in flower tissues than in roots and stems, and were not detectable in leaves. PhGRP transcripts were highest in stigma and style tissues, but were unaffected by exogenous ethylene treatment or pollination. PhGRP transcript levels fluctuated in a circadian rhythm with maximal accumulation late in the day.