Differential screening indicates a dramatic change in mRNA profiles duringgrape berry ripening. Cloning and characterization of cDNAs encoding putative cell wall and stress response proteins

We used differential screening to isolate ripening-associated cDNAs from a Shiraz grape (Vitis vinifera L.) berry cDNA library. A rapid increase in th e mRNA levels of a number of cDNAs not present in unripe fruit occurred in grape berries at the onset of ripening. The putative translation products o f some of these clones had homologs in other species that are involved in c ell wall structure. These included four proline-rich proteins, a small prot ein that is similar to the non-catalytic, N-terminal domain of some pectin methylesterases, and two other glutamate-rich proteins. The remainder of th e clones encoded putative stress response proteins. These included two thau matin like proteins, a metallothionein, a transcription factor, a cytochrom e P450 enzyme, and proteins induced by water, sugar, and/or cold stress in other species. Many of the homologs of the grape cDNAs thought to be involv ed in cell wall structure or stress-related responses also accumulate in a developmental manner in other plants. This may indicate that the grape mRNA s accumulate in response to stresses such as the storage of high concentrat ions of sugars and rapid cell expansion, or they may accumulate as part of the ripening developmental program.