Refinement of cDNA clone expression analysis in random sequencing from therapid cell development phase of citrus fruit

To characterize citrus fruit development, we analyzed changes in the levels of mRNAs in nine clones that included two glycine-rich protein (GRP) genes , an expressed sequence tag (EST) clone (EST1), and six putative stress-res ponsive genes (pcMFRI616.41, pcMFRI804.77, pcMFRI727.28, pcMFRI723.82, pcMF RI729.148 and pcMFRI804.36) during citrus development. GRPs were of two typ es; one clone (CitGRP 1) showed a high degree of identity to typical GRP ge nes, the other (CitRNA-GRP3) resembled the genes of glycine-rich RNA-bindin g proteins. The CitGRP1 transcript level was high in fruitlets, flowers, an d mature leaves, but decreased to low levels in the fruit during later deve lopment stages. The Cit-RNA-GRP3 transcript was present in all the plant or gans, except mature leaves. The EST1 transcript level was maximal in the ea rly development stage. Expression of the six putative stress-responsive gen es also was regulated distinctly, both temporally and spatially. Collective ly, the findings suggest that these genes have important roles in the norma l development and enlargement of citrus fruit and that they are regulated b y a wide range of internal and external stimuli.