Up-regulation of genes encoding novel extracellular proteins during fruit set in pea

The transition from the carpel of the flower to a developing fruit is a poo rly characterized process despite its agricultural importance. We have iden tified two genes, GIC19 and GIC4, which are expressed after induction of pe a (Pisum sativum L.) fruit set either by exogenous gibberellins or by polli nation. GIC19 expression is temporally and spatially regulated, with transc ripts mainly found in growing carpels and young fruit. Similar to GIC19, GI C4 expression is developmentally regulated during carpel and fruit developm ent. However, GIC4 transcripts are found in other growing tissues throughou t the plant. Analysis of their sequences and localization of fusion protein s with GFP indicate that both GIC19 and GIC4 are extracellular proteins. Wh ile GIC19 is a small proline-rich protein with no overall homology to other reported proteins, GIC4 belongs to a novel family of proteins. Our results reinforce a model of gibberellin mode of action during pea fruit set and d evelopment involving enhanced synthesis of extracellular proteins and secre tory activity to provide materials and energy for cell growth.