Genetic control and evolution of sesquiterpene biosynthesis in Lycopersicon esculentum and L. hirsutum.
Segregation analysis between Lysopersicon esculentum (cultivated tomato) and L. hirsutum (wild form) in conjunction with positional verification by using near-isogenic lines demonstrated that biosynthesis of two structurally different classes of sesquiterpenes in these species is controlled by loci on two different chromosomes. A locus on chromosome 6, Sesquiterpene synthase1 (Sst1), was identified for which the L. esculentum allele is associated with the biosynthesis of beta-caryophyllene and alpha-humulene. At this same locus, the L. hirsutum allele is associated with biosynthesis of germacrene B, germacrene D, and an unidentified sesquiterpene. Genomic mapping, cDNA isolation, and heterologous expression of putative sesquiterpene synthases from both L. esculentum and L. hirsutum revealed that Sst1 is composed of two gene clusters 24 centimorgans apart, Sst1-A and Sst1-B, and that only the genes in the Sst1-A cluster are responsible for accumulation of chromosome 6-associated sesquiterpenes. At a second locus, Sst2, on chromosome 8, the L. hirsutum allele specified accumulation of alpha-santalene, alpha-bergamotene, and beta-bergamotene. Surprisingly, the L. esculentum allele for Sst2 is not associated with the expression of any sesquiterpenes, which suggests that cultivated tomato may have a nonfunctional allele. Sesquiterpene synthase cDNA clones on chromosome 6 do not cross-hybridize on genomic DNA gel blots with putative sesquiterpene synthases on chromosome 8, an indication that the genes in Sst1 and Sst2 are highly diverged, each being responsible for the biosynthesis of structurally different sets of sesquiterpenes.
van Der Hoeven
R S
RS
Departments of Plant Breeding and Plant Biology, Cornell University, Ithaca, New York 14850, USA.
Monforte
A J
AJ
Breeden
D
D
Tanksley
S D
SD
Steffens
J C
JC
D000595:Amino Acid Sequence; D001483:Base Sequence; D002849:Chromatography, Gas; D017931:DNA Primers; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012717:Sesquiterpenes / Q000378:metabolism*; D013045:Species Specificity
D017931:DNA Primers; D007527:Isoenzymes; D012717:Sesquiterpenes; D011755:Pyrophosphatases