Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2005
Publication Date: 10/1/2005
Citation: Guo, B., Xu, G., Cao, Y. G., Holbrook, Jr., C. C., Lynch, R. E. 2006. Identification and characterization of phospholipase D and its association with drought susceptibilities in peanut (Arachis hypogaea). Planta. 223:512-520. Interpretive Summary: The production of quality peanut is the number one goal of the U.S. peanut industry since the majority of the peanuts produced in the U.S. are for human consumption. The most serious challenge to quality peanuts is preharvest contamination with aflatoxin, a potent cancer-producing toxin produced by the fungus called Aspergillus flavus. Aflatoxin contamination occurs when peanuts growing in the field are exposed to severe drought during the latter part of the growing season. The development of peanut lines with resistance to drought stress would represent a major advance for the peanut industry. Our research goal is to identify factors associated with resistance to aflatoxin, drought stress or insects, and to develop molecular markers to assist in the transfer of the resistance to commercial peanut lines. We have identified a novel gene called PLD (phospholipase D gene) that may well be associated with drought tolerance in peanut. It is the first such gene identified in peanuts and has characteristics similar to those identified in other crops for drought resistance. Additional study is needed, however, to characterize the gene and to develop markers for practical use in breeding.
Technical Abstract: Preharvest aflatoxin contamination has been identified by the peanut industry as the most serious challenge. Drought stress is the most important environmental factor exacerbating Aspergillus infection and aflatoxin contamination in peanut. Development of resistant peanut cultivars would represent a major advance for the U.S. peanut industry. In this study, we identified a novel PLD gene, encoding a putative phospholipase D, a main enzyme responsible for the drought-induced degradation of membrane phospholipids in plants. The completed cDNA sequence was achieved by using the consensus-degenerate hybrid oligonucleotide primer strategy. We have used the sequence information encoded by the cloned fragments to amplify both the 5' and 3' ends of this gene to obtain a full length sequence. The deduced amino acid sequence shows high identity with known PLD genes, having similar conserved features. The PLD gene expression under drought stress in greenhouse has been studied using four peanut lines, Tift 8 and A13 (both drought tolerant) and Georgia Green and 419A (both drought sensitive). Northern analyses had showed that PLD gene expression was induced faster by drought stress in the drought sensitive lines than the drought tolerance lines. Southern analyses show that there are 3 to 4 copies of this gene in peanut. More peanut lines will be studied to characterize the PLD gene expression as markers for screening germplasm for drought tolerance and aflatoxin formation.