LIU, XIANAN*, AHMED BAHIELDIN, EL-SAYED HASSANEIN, MOHAMED EL-DOMYATI, SHERIF EDRIS, AND WM. VANCE BAIRD. Horticulture Department, Clemson University, Clemson, SC 29634-0375; and Department of Genetics, Faculty of Science, Ain Shams University, Cairo, Egypt. - Identification and characterization of genes from sunflower (Helianthus annuus L.) that are regulated by drought or osmotic stress.
Negative effects on the water status of plants is one of the most
common and deleterious stresses experienced by wild and cultivated
plants throughout the world. Sunflower is the second most important
edible oil crop on a worldwide production basis. In the middle-east,
insufficient water or irrigation of sunflower using salt-contaminated
water from rivers or reservoirs is a major problem for field
establishment and final crop production. Our project is designed to
identify, clone and characterize gene sequences regulated in response
to water stress (e.g., drought and/or salinity). We employed the
differential-display reverse transcriptase polymerase chain reaction
(DD-RT-PCR) methodology to accomplish our objectives. To date five
drought-regulated and ten salinity-regulated gene sequences have been
cloned. These represent genes that are either induced de novo,
up-regulated or down-regulated in response to water stress, and
preliminary evidence shows that individual transcripts may be present
in all tissues/organs or expressed specifically in roots, shoots or
leaves. Sequence analysis has tentatively identified genes for at
least five clones: guanylate kinase (Cap1-1U), an enzyme important in
second messenger signaling pathways; selenium binding protein
(GAp1-D), also implicated in ABA-response; activator-encoded
transposase (CAp2-U), an essential factor for the mobility of Ac-like
elements; polyprotein (RSG10-U), a retrotransposon-associated reverse
transcriptase-like sequence; and LytB (VC2-D), a pneumococcal murein
hydrolase important in cell-division. Current efforts focus on
acquiring full-length cDNA and genomic clones, identifying and
characterizing their cis-acting regulatory elements and
trans-acting factors, precisely defining expression patterns on
a tissue and temporal basis, and determining the in vivo
biochemical/physiological function of the proteins encoded by each
gene clone.
Key words: differential display, drought stress, osmotic stress, salt stress, sunflower