Genetics and tomato size

[coronabarb]

An interesting article about a scientist's quest to find how wild tomatoes ended up so big...

http://news.yahoo.com/s/nm/20080511/...es_tomatoes_dc

[Raymondo]

Now that they appear to know the responsible gene(s), I wonder if they could take a wild currant type, tweak it, and instantly create a beefsteak version!

[carolyn137]

This same article also appeared at the new SSE message site page this AM and I read it through there.

I also posted there the current list of tomato species of which there are now 17, all with the genus name of Solanum. it's in my faves back on AOL so if anyone is interested let me know and I can transfer it over here.

It's really quite misleading to say just wild tomato b'c of the 17 species all but one, our garden tomato, are small mostly inedible species. The only species that are commonly eaten are Solanum lycopersicum, our garden tomato, and S. Pimpinellifolium, the currant tomato, and a few folks grow S. cheesmanii from time to time.

My point being that it's only the progenitor of our garden tomato that was upsized and all of the others remain small sized.

ON Saturday I had two guests from the USDA station at Geneva, NY and both Angela Baldo and Joanne Labante are doing work with the species and our garden tomato to see how much DNA there is from the species in our garden tomato. Angela is a Ph.D computational type person while Joanne, also a Ph.D is a molecular biologist.

I kept pushing them to explain to me why small fruit size is dominant to large size and we had a spirited conversation, I can tell you that. LOL

This is the third time I've met with them ( last year it was in the hospital 2 days after my new right hip and femur fracture, Sigh) and it's b'c Joanne has relatives in Granville and Queensbury ( Glens Falls) so they drive to this area a couple of times each year, and this time Joanne was here for Mother's Day.

I just wish that in the article they'd used the terms locules instead of "wells".

A very interesting article indeed. Tanksley, who was mentioned in the article, is head of the tomato gene project at Cornell, well not just at Cornell for there are other members in other countries who are participating but he's head of the Tomato GEne Project worldwide, and the Geneva Station where Angela and Joanne are is an extension of Cornell and both have adjunct faculty appts at Cornell at Ithaca.

Craig and I both know Joanne and Angela b'c Angela went fishing at GW quite a few years ago looking for folks who had large collections of OP varieties that they needed for their project and we've been designated as consultants to the project in terms of grant applications to the Feds.

[dice]

An interesting question here is what makes any gene
dominant or recessive? What is the actual chemical
mechanism of genetic dominance in gene pairs? Is it
always the same for any dominant-recessive gene
combination?

[tomatoguy]

You know, a couple of things really trouble me about this article. First, click on the picture on the left. This is either a joke or the farmer in the picture is smaller than Tom Thumb or the tomatoes are the size of watermelons. I lean toward the joke scenario. I'm surprised they aren't blue as well. Secondly, I detect more than a small note of condescension in this quote: "What's marvelous is that humans did this with no knowledge of genetics ... yet the impact was so enormous," Okay, just because these folks were not scientists and Mendel hadn't even been born yet, believe me they had a practical knowledge of genetics, perhaps beyond what most of us now know. If they didn't, explain to me the domesticated cotton plant or the many varieties of domesticated dog for that matter. This sort of scientific chauvinism reminds me of the Eurocentric history I was taught as a child where nothing was "discovered" until it was found by a Caucasian.

mater

[coronabarb]

I don't see the picture as a joke...it's just the way the camera took the picture...the tomatoes are close, the farmer is farther away.

[Tom Wagner]

• genes code for proteins.
• a protein will be made that does a particular job in the cell
• acts as an enzyme or a structural protein.
• "Dominant" refers to an active gene / protein,
• a dominant allele codes for a protein that works.
• A Recessive gene is one that codes for a protein that doesn't do the job as well
• You don't notice the effect of the recessive gene) or does the job partially
• there can be several different versions of an allele that are dominant. Hence you get gradations producing a mix of slightly different but still effective proteins.
• Recessive disorders tend to result from failures (mutations) in genes that code for enzymes

What makes a gene a 'dominant' gene?

• Dominant gene are traits thatwill be observerd in the organisms appearance or physiology.
• The recessive cannot be observed unless the individual has two copies of the recessive alleles
• Dominant means stronger
• a dominant gene has a more efficient allele and DNA sequence than a recessive gene.
• something to do with the way that the alleles are arranged or mutated.
• Most genes are called "wild" if they are the normal gene expressed at that section of the allele pair. Read "common" or "normal" and anything that is not normal is like a mutation of that gene, often lacking some information or protein messengers.

The information above is in response to Dice's question:

An interesting question here is what makes any gene
dominant or recessive? What is the actual chemical
mechanism of genetic dominance in gene pairs? Is it
always the same for any dominant-recessive gene
combination?

Tom Wagner

[dice]

Thanks, Tom, for the explanation.

So, are there any big tomatoes (like 8oz or bigger)
with only 2 locules? (Just curious.)

[barkeater]

dice, if there is, it's the world record for a cherry tomato! ;-)

[Tom Wagner]

T

hanks, Tom, for the explanation.

So, are there any big tomatoes (like 8oz or bigger)
with only 2 locules? (Just curious.)

Dice,

Yes, I have made selections for big fruit and only 2 locules, but those lines were put away in the seed bank as oddities. They were way too seedy for my likes and wishes. Most of the lines that would throw that phenotype also would occasionally form 3 locules.

The more interesting ones with that trait are the hollow stuffing types with thin walls and (strawberry seed clusters) in the center. These phenotypes are so light as to convince one that they are not tomatoes.

Tom W.

[Raymondo]

I did say 'currant type'. Okay, okay, I should have been specific. So, let me put the question again.
Now that the responsible gene(s) for larger fruit size have been identified, would it be possible to simply tweak the relevant gene(s) in S. pimpinellifolium and get something larger straight away, well, next generation? I guess I'm asking whether this gene (these genes) are in S. pimpinellifolium's genome.

[carolyn137]

Originally Posted by Raymondo

I did say 'currant type'. Okay, okay, I should have been specific. So, let me put the question again.
Now that the responsible gene(s) for larger fruit size have been identified, would it be possible to simply tweak the relevant gene(s) in S. pimpinellifolium and get something larger straight away, well, next generation? I guess I'm asking whether this gene (these genes) are in S. pimpinellifolium's genome.

Ray, I've read so much in this area recently that I've forgotten much of what I've read and where I read it.

And I'm confused a bit b'c if the relevant genes are in S. pimpinellifolium what changes the expression such that that species is still maintained as a disctinct species?

And yes, I do know that small bits of pimp DNA has been found in larger fruited varieties, but I don't remember if in all that were tested or the exact numbers.

But I think I will be able to get some answers directly from the person who IDed the upsizing genes who is Dr. Esther van der Knapp at Ohio State University. And without spinning a long story I was asked to do part of a chapter in a new academic book on the value of OP heirlooms to breeders, but gently said no. I found someone else to do it and then that didn't work out, so they found someone new to do it, which is Dr. van der Knapp and she's been asked to run her article by me for opinions and input.

So I have her contact info as of yesterday and after she writes what she's going to write, which has first priority to meet a deadline, I won't hesitate to ask her some of these questions.

And I do think in all the stuff I read that yes, taking the relevant genes out of pimp can upsize an accession, but I can't point you to a specific reference source right now.

I do remember running across a paper by Zach Lippman and Dr. Stevce Tanksley who is head of the tomato genome project, from 2001, where these initial observations were made and in that paper there was a personal communication from Esther sharing her info as well.

Now the interesting thing about that paper is that Zach Lippman got his Ph.D with Tanksley and went to Israel for a post doc and his project there necessitated him growing out 1000 different heirloom varieties to look for DNA fingerprint tracks from other species.

I can't remember exactly who gave Zach my contact info but I had to round up Craig and Glenn Drowns so that we could come up with seed that was fairly fresh for 1000 varieties. What I do remember is that it was just after I fell in Dec of 2004 and severed all four of the quad muscles in my right leg and it was a real bummer trying to work with my seeds to get those out to Zach. And at the same time I'd made a huge seed offer in late Fall of 2004 at GW with about 150 different varieties and about 200 folks responded and I was literally going nuts trying to get those out as well. Sigh.