1a. Objectives (from AD-416):
The objectives of this project are: 1) to identify and compare expression of genes in apple and grape that respond to both biotic and abiotic stress; and 2) to identify and compare regulatory regions (promoters) of apple and grape homologs to find differences and similarities.
1b. Approach (from AD-416):
Most of the approach will involve bioinformatic (ARS role) methods and verification by expression analysis (Cooperator role). Stress responsive genes expressed in apple in response to cold and drought will be compared with genes from grape responding to fungal disease infection (Cooperator). Common sets of genes identified in both species will be further analyzed using existing genome resources to find the promoter regions of the genes in grape and those in apple and compare the cis-elements that contribute to their regulation (ARS). Promoter discovery software will be used to identify the cis-elements found in both apple and grape promoters. Functional tests using select promoters controlling a reporter gene will verify the roles they play during exposure to biotic or abiotic stress (ARS and Cooperator).
3. Progress Report:
Plants are subjected to numerous environmental stresses caused by extreme weather patterns, including high and low temperatures, periods of no rainfall or too much rainfall, and mechanical damage caused by wind and hail. Because studies of recent climate changes predict increased drought episodes, there is an immediate need to develop crops that can survive long periods of limited rainfall. This need is especially critical for fruit and nut trees because orchard plantings are expected to survive and produce for decades. Increasing the water use efficiency of these crops would also lower irrigation requirements and reduce competition for water resources in nearby urban areas. Many plants have been able to adapt to periods of extreme weather stress by creating new sets of genes with altered expression. These genes are poised to respond to a variety of stress events, and because they are associated with survival on land, they are well conserved in most higher plants, including important crops. Studing the differences and similarities in the expression of these stress-responsive genes in related crops, such as apple and grape, will help identify which genes contribute the most to drought tolerance. The objective of this collaborative arrangement (grape studies at NAFU and apple studies at AFRS) is two-fold: 1) to identify and compare expression of genes in apple and grape that respond to both biotic and abiotic stress and 2) to identify and compare regulatory regions (promoters) of apple and grape homologs to find differences and similarities. Identified a family of genes in apples that is associated with early response to a number of environmental stresses. This family, SBP-box (Squamosa binding protein), consists of 27 members, many of which were responsive to well known plant stress hormones. A paper describing these results was recently accepted for publication in a peer-reviewed journal. We plan to continue these studies to include comparison of the promoter regions of the individual family members to identify sequences responsible for regulation of the expression of these genes. We have also identified a family of 50 genes involved in protein degradation in grape. The enzymes encoded by these genes belong to the Aspartic Protease (AP) class and appear to function both in stress responses as well as during plant development. Protein turnover is a key mechanism for regulating the final expression of a given gene. Fifty different genes encoding Aps in grape were identified and their expression in response to various stress treatments determined. Some family members were more responsive to drought than salt, while others were more responsive to salt. Expression in response to the plant stress hormones was also determined with some overlap in response observed. A manuscript describing the different grape family members and their expression in response to drought and salt treatment is currently being revised in preparation for publication.