Pleiotropic Genes in Tomato

[jcm05]

My understanding is this type of gene can influence multiple phenotypic traits in crosses. What are some examples of them? Any common ones?

[hillbillypie]

If tomatoes work like people I would think that Pleiotropic genes would only work at the physiological/biochemical level. It's my understanding that pleiotropy is where one gene serves to produce something that is used in more than one place within a biological system. It wouldn't surprise me if sugars in fruit were that way. Also the malic acid, citric acid, and all of the volatiles could be pleiotropic. That's some complicated genetics stuff there. (walk away slowly ;D) Been too long since that kept me up at night and it had no foundation in plant genetics when it did. Perhaps if you google Phenylketonuria, you might have a better understanding of the process in general since this is probably the most studied and well known instance of that type of gene function.

--S.

[frogsleapfarm]

Pleiotropic genes affect/control more than one phenotypic trait. The y locus controls yellow vs clear epidermis (e.g. red vs pink fruit color), and also affects elasticity of the epidermis which is one factor in resistance to radial cracking.

[gobmaters]

The crimson gene (ogc) and the tangerine gene (t) affect both flower color and fruit color, and the flower color can be used to determine presence of these recessive genes in homozygous condition when the plant flowers rather than having to wait til fruit ripening to make a determination. The I-3 gene for fusarium wilt race resistance gives a darker green, taller growing, and more open plant than in plants without the I-3 gene. I often use this to predict which plants will have the I-3 gene. Plants with the I-3 gene also have smaller fruit size and are more susceptible to blossom end rot than plants without the I-3 gene. Sometimes what is considered pleiotropy may be the result of very tight gene linkage rather than the same gene controlling expression of different traits in the plant. When going back to wild species for various traits, deleterious pleiotropic effects are often seen associated with many genes. This has occurred for root knot nematode resistance, verticillium wilt resistance, TMV resistance , and insect resistance in tomato. In many instances, however, after the genes were worked with long enough, it turned out that the deleterious traits were in fact resulting from closely linked genes, which just took a lot of crossing to finally shorten the chromosome segment coming from the wild species and get rid of the deleterious linked genes. This may turn out to be the case for some of the undesirable traits associated with the I-3 gene since it is a fairly recent gene transferred from a wild species.

[grunt]

ARS published this today www.ars.usda.gov/is/pr/2011/110201.htm