Poster: Secondary Metabolism

Abs # 287: Capsaicinoid biosynthesis: candidate structural and regulatory genes

Presenter:	O'Connell, Mary A., moconnel@nmsu.edu
Authors	O'Connell, Mary A. (A)   Curry, Jeanne  (A)   McManus, Laura  (A)   Aranda, Erick R. (A)
Affiliations:	(A): Department of Agronomy and Horticulture, New Mexico State University

Capsaicinoid biosynthesis is uniquely found in members of the genus Capsicum. The capsaicinoids, responsible for the “heat” or pungency, accumulate in the epidermal layer of the placenta. There is qualitative control of this phenotype exerted by the single dominant locus C for the ability to be pungent, and there is quantitative control of this phenotype, controlling the degree of pungency among pungent genotypes. We have isolated and characterized a number of cDNAs which encode candidate genes for ~10 different biosynthetic steps on the capsacinoid biosynthetic pathway and cDNAs for two different transcription factors. We have expressed recombinant forms of these proteins to raise antibody. We have isolated the promoter regions for two genes on the branched chain fatty acid portion of the biosynthetic pathway, Acl, and Fat, and two genes on the phenylpropanoid portion of the capsaicinoid biosynthetic pathway, Ca4h, and Comt. These promoters have been isolated from three different pungent varieties, habanero, Joe E. Parker, New Mexico 6-4, and four different non-pungent varieties, Jupiter Bell, Conquistador, and non-pungent jalapeno and habanero. These genomic promoter sequences range in size from 100 to 800 bp upstream of the ATG start. We have collected populations of individual gene walking products to control for the amplification of allelic variants and gene family members. DNA sequence alignments have identified promoter variants that include single nucleotide changes as well as indels. We expect to be able to relate promoter elements conserved among the coordinately regulated genes identified by RNA expression analyses. This work was supported by the NM Agricultural Experiment Station and NIH grant S06 GM 08136.