Refinement of cDNA Clone Expression Analysis in Random Sequencing from the Rapid Cell Development Phase of Citrus Fruit

Abstract

Summary 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-responsive genes (pcMFR1616.41, pcMFR1804.77, pcMFR1727.28, pcMFRI729.82, pcMFRI729.148 and pcMFR1804.36) during citrus development. GRPs were of two types; one clone (CitGRPI) showed a high degree of identity to typical GRP genes, the other (CitRNA-GRP3) resembled the genes of glycine-rich RNA-binding proteins. The CitGRP 1 transcript level was high in fruitlets, flowers, and mature leaves, but decreased to low levels in the fruit during later development stages. The CitRNA-GRP3 transcript was present in all the plant organs, except mature leaves. The EST 1 transcript level was maximal in the early development stage. Expression of the six putative stress-responsive genes also was regulated distinctly, both temporally and spatially. Collectively, the findings suggest that these genes have important roles in the normal development and enlargement of citrus fruit and that they are regulated by a wide range of internal and external stimuli.