TY - JOUR
T1 - Epistasis in tomato color mutations involves regulation of phytoene synthase 1 expression by cis-carotenoids
AU - Kachanovsky, David E.
AU - Filler, Shdema
AU - Isaacson, Tal
AU - Hirschberg, Joseph
PY - 2012/11/13
Y1 - 2012/11/13
N2 - Tomato (Solanum lycopersicum) fruit accumulate the red carotenoid pigment lycopene. The recessive mutation yellow-flesh (locus r) in tomato eliminates fruit carotenoids by disrupting the activity of the fruit-specific phytoene synthase (PSY1), the first committed step in the carotenoid biosynthesis pathway. Fruits of the recessive mutation tangerine (t) appear orange due to accumulation of 7,9,7′,9′-tetra-cis-lycopene (prolycopene) as a result of a mutation in the carotenoid cis-trans isomerase. It was established 60 y ago that tangerine is epistatic to yellow-flesh. This uncharacteristic epistasis interaction defies a paradigm in biochemical genetics arguing that mutations that disrupt enzymes acting early in a biosynthetic pathway are epistatic to othermutations that block downstream steps in the same pathway. To explain this conundrum, we have investigated the interaction between tangerine and yellow-flesh at the molecular level. Results presented here indicate that allele r2997 of yellow-flesh eliminates transcription of PSY1 in fruits. In a genetic background of tangerine, transcription of PSY1 is partially restored to a level sufficient for producing phytoene and downstream carotenoids. Our results revealed the molecular mechanism underlying the epistasis of t over r and suggest the involvement of cis-carotenoid metabolites in a feedback regulation of PSY1 gene expression.
AB - Tomato (Solanum lycopersicum) fruit accumulate the red carotenoid pigment lycopene. The recessive mutation yellow-flesh (locus r) in tomato eliminates fruit carotenoids by disrupting the activity of the fruit-specific phytoene synthase (PSY1), the first committed step in the carotenoid biosynthesis pathway. Fruits of the recessive mutation tangerine (t) appear orange due to accumulation of 7,9,7′,9′-tetra-cis-lycopene (prolycopene) as a result of a mutation in the carotenoid cis-trans isomerase. It was established 60 y ago that tangerine is epistatic to yellow-flesh. This uncharacteristic epistasis interaction defies a paradigm in biochemical genetics arguing that mutations that disrupt enzymes acting early in a biosynthetic pathway are epistatic to othermutations that block downstream steps in the same pathway. To explain this conundrum, we have investigated the interaction between tangerine and yellow-flesh at the molecular level. Results presented here indicate that allele r2997 of yellow-flesh eliminates transcription of PSY1 in fruits. In a genetic background of tangerine, transcription of PSY1 is partially restored to a level sufficient for producing phytoene and downstream carotenoids. Our results revealed the molecular mechanism underlying the epistasis of t over r and suggest the involvement of cis-carotenoid metabolites in a feedback regulation of PSY1 gene expression.
KW - Fruit development
KW - Tomato breeding
UR - http://www.scopus.com/inward/record.url?scp=84869232168&partnerID=8YFLogxK
U2 - 10.1073/pnas.1214808109
DO - 10.1073/pnas.1214808109
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C2 - 23112190
AN - SCOPUS:84869232168
SN - 0027-8424
VL - 109
SP - 19021
EP - 19026
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 46
ER -