Genome sequencing reveals what puts the ‘heat’ in hot peppers

The genome of the hot pepper, the worlds most widely grown spice crop, has been sequenced by a large international team of researchers, including scientists at the University of California, Davis.

The new reference genome sheds light on the biology of the peppers hallmark pungency, or spiciness, as well as its fruit-ripening and disease-resistance mechanisms.

It also reveals new information crucial for improving the horticultural, nutritional and medicinal qualities of these peppers, whose annual global production has grown more than 40-fold during the past two decades and now exceeds $14.4 billion.

Highlights from the sequencing effort were reported Jan. 19 as an Advanced Online publication of the journal Nature Genetics.

The pepper genome is one of the largest genomes assembled to date, said plant scientist Allen Van Deynze, director of research at UC Davis Seed Biotechnology Center and a co-author on the study.

The quality of this genome assembly and linkage to the high-density genetic map for peppers makes the genes and genome immediately available to the genetics community, he said.

Hot peppers, one of the oldest domesticated crops in the Western Hemisphere, are members of the Solanaceae plant family and thus cousins to an extensive group of plants including potato, tomato, eggplant, petunia and tobacco. The hot-pepper plants are popular ornamentals and produce fruits that are major vegetables in most global cuisines, as well as rich sources of vitamins and nutrients, pharmaceuticals, natural coloring agents, cosmetics and defense repellants.

The researchers sequenced a hot pepper landrace, or domesticated variety, from the Mexican state of Morelos. The variety, known as Criolo de Morelos 334, has consistently exhibited high levels of disease resistance and has been extensively used in hot-pepper research and breeding. The research team also provided sequencing data for the Perennial and Dempsey cultivated pepper varieties and for the related habanero pepper species (Capsicum chinense.)

Not surprisingly, the new sequencing project revealed that blocks of genes appear in much the same chromosomal position in the hot pepper as in its closest relative, the tomato. The pepper genome, however, was found to be 3.5-fold larger than the tomato genome.

The sequencing also uncovered evidence suggesting that the pungency, or heat, of the hot pepper originated through the evolution of new genes by duplication of existing genes and changes in gene expression after the peppers evolved into species.

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Genome sequencing reveals what puts the ‘heat’ in hot peppers