Plant biochemist Ann Powell checks on green and ripe tomato fruit that naturally carry genes for more sugars, soluble solids and the health-promoting compound lycopene. Barbara Blanco-Ulate/UC Davis photo
new discovery could make more tomatoes taste like heirlooms, reports an
international research team headed by a University of California,
Davis, plant scientist.
finding, which was reported in the June 29 issue of the journal
Science, has significant implications for the U.S. tomato industry,
which annually harvests more than 15 million tons of the fruit for
processing and fresh-market sales.
information about the gene responsible for the trait in wild and
traditional varieties provides a strategy to recapture quality
characteristics that had been unknowingly bred out of modern cultivated
tomatoes,” said Ann Powell, a biochemist in UC Davis’ Department of
Plant Sciences and one of the lead authors of the study.
that we know that some of the qualities that people value in heirloom
tomatoes can be made available in other types of tomatoes, farmers can
have access to more varieties of tomatoes that produce well and also
have desirable color and flavor traits,” she said.
decades, plant breeders in the tomato industry have selected varieties
that are uniformly light green before they ripen, in order to produce
tomatoes that can be harvested at the same time.
this characteristic is accompanied by an unintended reduction in sugars
that compromises the flavor of the fresh fruit and its desirability for
UC Davis research team began studying the genes influencing tomato
fruit development and ripening after spending two summers screening
tomato plants for transcription factors that might play a role in both
fruit color and quality. Transcription factors are proteins that
regulate genes, or turn them on and off. These factors themselves are
manufactured or expressed by genes.
UC Davis researchers were particularly interested in tomatoes they
observed in the field that were unusually dark green before they
with researchers at Cornell University and in Spain, who were mapping
regions of the tomato genome, the scientists discovered two
transcription factors, called GLK1 and GLK2, that control the
development of chloroplasts. Chloroplasts are the structures in the
plant cells that enable plants to photosynthesize, converting the energy
of sunlight into sugars and other compounds that influence flavor and
researchers scoured a collection of mutant and wild species of tomatoes
at UC Davis established at UC Davis by the late Professor Charles Rick
beginning in the 1950s. They discovered that dark green tomatoes that
naturally express GLK2 produced ripe fruit with increased levels of
sugars or soluble solids, important for processing tomatoes, as well as
higher levels of the health-promoting compound lycopene.
presents numerous important genes and their variants, like uniform
ripening, that breeders employ to facilitate the needs of growers,
processors and consumers,” said Jim Giovannoni, a USDA plant molecular
biologist with the Boyce Thompson Institute at Cornell University.
“Understanding the genes responsible for these characteristics
facilitates the challenging process of breeding crops that meet the
needs of all components of the food-supply chain.”
Nguyen, a Cornell graduate student in Giovannoni’s laboratory
co-authored the paper with Powell. Other members of the research team
included: Theresa Hill, KaLai Lam Cheng, Rosa Figueroa-Balderas, Hakan
Aktas, Hamid Ashrafi, Ariel Vicente, Javier Lopez-Baltazar, Roger
Chetelat, Allen Van Deynze and Alan Bennett, all of UC Davis; Yongsheng
Liu and Cornelius Barry of Cornell University and the Boyce Thompson
Institute of the USDA; Clara Pons and Antonio Granell, of the
Universidad Politécnica de Valencia, Spain; Rafael Fernández-Muñoz of
the Universidad de Málaga, Spain.
for the study was provided by The University of California Discovery
program, the U.S. Department of Agriculture-Agricultural Research
Service, the National Science Foundation, the Viet Nam Education
Foundation, the Fundación Genoma España, and the Ministerio de Ciencia y
Tecnología and the Instituto Tecnólogico de Costa Rica.
Davis is an international leader in agricultural research and is ranked
as the most frequently cited university in the world in the area of
plant and animal sciences, according to ISI Essential Science
Indicators. The university’s Department of Plant Sciences is
internationally known for its Plant Breeding Academy, which provides
professional training for plant breeders around the world.
Source: University of California Davis