A FAMILY OF WOUND-INDUCED GENES IN POPULUS SHARES COMMON FEATURES WITH GENES ENCODING VEGETATIVE STORAGE PROTEINS

Two wound-inducible cDNAs from poplar leaves show sequence identity to vegetative storage proteins (VSP) that accumulate seasonally in popla r bark tissues. We have compared the genomic organization, cDNA sequen ces and expression of the genes encoding the wound-inducible cDNAs (wi n4) with that of a bark VSP (called bark storage protein, or BSP). The re appear to be several win4 genes in the poplar genome which segregat e as a single locus and are therefore likely to be clustered. The same is true of the BSP genes. The win4 locus is linked (map distance of 5 cM) to the BSP locus, consistent with a common evolutionary origin of the genes. A near full-length win4 cDNA shows 75% sequence identity t o BSP cDNAs. Both win4 and BSP are systemically wound-inducible; win4 transcripts accumulate in leaves and stems, whereas BSP transcripts ac cumulate almost exclusively in stems. A phloem transport-dependent sig naling mechanism appears to be involved in systemic win4 expression af ter wounding. In contrast to BSP gene expression, win4 genes are not e xpressed in response to short day conditions. The data indicate win4 a nd BSP genes are differentially regulated, and their products may play important roles in the storage and reallocation of nitrogen in perenn ial plants.