Drought-Responsive Genes in Populations From Desert Habitats

Project Number:

97R-13

Project Duration:

36 Months

Dates:

May 1, 1997 to April 30, 2000

Institution of Principle Investigator while on this project:

Ben-Gurion University of the Negev

Investigators (most current known information)

Novoplansky, Ariel (PI)

Lecturer, Ben-Gurion University of the Negev, Institute for Desert Research, Dept. of Life Sciences, Sede Boker 84990, ISRAEL

TEL: +972-8-653-2064, FAX: +972-8-659-6704, Email: anovopla@bgumail.bgu.ac.il

O'Connell, Mary

Professor, Department of Agronomy & Horticulture, New Mexico State University, Box 3Q, PO Box 30003, Las Cruces NM 88003

TEL: +1-575-646-5172, FAX: +1-575-646-6041, Email: moconnel@nmsu.edu

Proposal Abstract

The overall goal of this project was to describe the variability in different populations of desert forage plants, Dactylis glomerata and Trifolium purpureum. Plants collected in the Mediterranean region of Israel represent core populations, while plants collected in the Negev desert/non-desert transition zone in Israel represent peripheral populations. The Israeli team characterized the plants at the organismal and physiological level. The U.S. team characterized the plants at the molecular genetic level.

To test the hypothesis that the genetic complexity for drought response genes is greater in peripheral vs core populations of plants the structures of gene families for a number of drought responsive and non-responsive genes were evaluated. Genomic DNA was isolated from leaf tissue and Southern blots prepared from 120 individuals from each species. These individuals represented three sites in the peripheral region and three sites in the central region (20 individuals/species/site). To obtain drought-responsive gene sequences to use as probes on the Southern blots, cDNA libraries of transcripts in drought-stressed leaves were prepared from each species and screened to obtain drought induced, drought-repressed and drought neutral genes.

Six drought-induced genes, four repressed genes and three neutral genes were used as probes in the Restriction Fragment Length Polymorphism (RFLP) analysis of Dactylis. Genetic diversity for drought-responsive genes is greater in peripheral populations of Dactylis glomerata than in central populations. Drought neutral genes had less genetic diversity than drought-responsive genes and for this class of genes the diversity was greater in the central population. Two drought-induced genes, three repressed genes, and two neutral genes were used as probes in the RFLP analysis of Trifolium. Again the results suggested that genetic diversity for drought-neutral genes in Trifolium is less than for drought-responsive genes although the statistical support for this trend was limited. In both species, the within population variation accounted for most of the variation.