M.S. Exit Seminar

Nov 14, 2014, 1:00pm - 2:00pm
Deadline: 

Caleb Orchard

Advisor: Dr. David Francis
Committee: Dr. Leah McHale, Dr. Joseph Scheerens, Dr. Steven Schwartz

Naturally occurring variation in the promoter of the chromoplast-specific Cyc-B gene in tomato can be used to modulate levels of β-carotene in ripe tomato fruit

Abstract

β-carotene is an important carotenoid for human health due to its pro-vitamin A activity. While many carotenoids exhibit provitamin A activity and are available in food crops, nevertheless, Vitamin A deficiency remains the leading cause of preventable blindness in many developing countries. In tomato (S. lycopersicum, L.), the B gene (Cyc-B) encodes a chromoplast-specific lycopene-β-cyclase that converts trans-lycopene to β-carotene. Prior research suggests that DNA sequence variation in the promoter of B may be responsible for the high β-carotene Beta phenotype. We examined the carotenoid profiles of vintage and contemporary tomato varieties to identify sources of high β-carotene. Red tomatoes had a range from 0.2 – 0.97 mg/100 g fresh weight of β-carotene, while several orange-fruited varieties had 1.67 – 4.0 mg/100 g. The non-transcribed region 5′ to the B gene (promoter) contains significant nucleotide variation, with ten unique haplotypes across 1850 bp of sequence. Sequence analysis suggested that the B promoter was derived from wild tomato species. Association mapping and non-parametric statistical approaches suggest two single nucleotide polymorphisms (SNPs) as the most likely cause(s) of high β-carotene, presumably through their influence on transcription of the gene. A marker-assisted backcross breeding scheme leveraging genome-wide SNPs was used to rapidly develop a series of genetic resources containing different alleles of the B promoter in a uniform genetic background. Replicated field trials demonstrated that distinct alleles can be used to modulate the levels of β-carotene in tomato. These genetic resources are available to develop β-carotene enriched food products or to study dietary adsorption and utilization of carotenoids in the food matrix. Furthermore, studying the basis of variation in carotenoid biosynthesis in general, and specifically β-carotene, provides a clearer understanding of biochemical regulation and phenotypic variation in plants.

Friday November 14th, 2014
1:00 PM – 2:00PM

123 Williams (Wooster) video linked to
Kottman Hall 202F (Columbus)