Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol

Abstract

Global cottonseed production can potentially provide the protein requirements for half a billion people per year; however, it is woefully underutilized because of the presence of toxic gossypol within seed glands. Therefore, elimination of gossypol from cottonseed has been a long-standing goal of geneticists. Attempts were made to meet this objective by developing so-called ''glandless cotton'' in the 1950s by conventional breeding techniques; however, the glandless varieties were commercially unviable because of the increased susceptibility of the plant to insect pests due to the systemic absence of glands that contain gossypol and other protective terpenoids. Thus, the promise of cottonseed in contributing to the food requirements of the burgeoning world population remained unfulfilled. We have successfully used RNAi to disrupt gossypol biosynthesis in cottonseed tissue by interfering with the expression of the ␦-cadinene synthase gene during seed development. We demonstrate that it is possible to significantly reduce cottonseed-gossypol levels in a stable and heritable manner. Results from enzyme activity and molecular analyses on developing transgenic embryos were consistent with the observed phenotype in the mature seeds. Most relevant, the levels of gossypol and related terpenoids in the foliage and floral parts were not diminished, and thus their potential function in plant defense against insects and diseases remained untouched. These results illustrate that a targeted genetic modification, applied to an underutilized agricultural byproduct, provides a mechanism to open up a new source of nutrition for hundreds of millions of people.food safety ͉ gene silencing ͉ RNAi ͉ seed-specific promoter ͉ terpenoids

The draft genome of a diploid cotton Gossypium raimondii

“…Diploid cotton species share a common chromosome number (n = 13), and high levels of synteny or colinearity are observed among them [9][10][11][12] . The tetraploid cotton species (2n = 4× = 52), such as G. hirsutum L. and Gossypium barbadense L., are thought to have formed by an allopolyploidization event that occurred approximately 1-2 million years ago, which involved a D-genome species as the pollen-providing parent and an A-genome species as the maternal parent 13,14 . To gain insights into the cultivated polyploid genomes-how they have evolved and how their subgenomes interact-it is first necessary to have a basic knowledge of the structure of the component genomes.…”

Gossypol: phytoalexin of cotton

“…Transgenic technology has also been employed to produce new valuable germplasms. By seed-specific suppression of the CDN expression, plants of ultra-low gossypol cottonseed (ULGCS) were developed (Sunilkumar et al, 2006), and field trial results confirmed the stability and specificity of the ULGCS trait, suggesting that this RNAi-based product has the potential to be commercially viable (Palle et al, 2013).…”

Molecular cloning and expression analysis of GhLOF genes in upland cotton (Gossypium hirsutum L.)

“…It is planted in more than 80 countries by about 20 million farmers, and occupies approximately 5% of the world's arable land (Sunilkumar et al, 2006;Wang et al, 2012). Branching pattern is an important agronomic trait of cotton, and understanding the molecular basis of cotton branching will help develop compact cotton varieties that are suitable for mechanized harvesting, through the modulation of the plants' architecture.…”