Good smelling tomatoes
Nobody wants a juicy tomato with no taste. Still breeders managed to get those when selecting for pest resistant varieties with bigger tomatoes. Over the years it has become clear that volatile molecules coming from the tomato are just as big as a contributor to the flavour of tomatoes as the flavour molecules in the tomatoes themselves. But giving those volatiles back turned out not as easy as it sounds. Now a group of Korean researchers found out that losing a single gene that regulates the degradation of chloroplasts also influences the production of volatile molecules.
STAY-GREEN1 is the name of that gene that regulates chloroplast degradation. In its absence leaves are staying green and active for longer, as if they defy the natural aging process. The fruits of tomato plants without STAY-GREEN1, which do ripen and turn red, also have a longer shelf life. But if this actually translates into a tomato with a richer scent pattern was unknown.
More scent molecules
To find out the researchers analysed the volatile molecules from six stages of ripening tomatoes with and without STAY-GREEN1. The first thing they noticed was that the volatile profile of the tomatoes with STAY-GREEN1 at each of the ripening stages was different from the profile of tomatoes without STAY-GREEN1. But that was not all, the tomatoes without STAY-GREEN1 produced also more volatiles. These differences resulted in that the over ripe tomatoes without STAY-GREEN1 had a completely different volatile profile that over ripe tomatoes with STAY-GREEN1.
To investigate this in more detail the researchers analysed the how active the genes were that are involved in the production of these volatiles. Some of the genes did not show any differences between tomatoes with and without STAY-GREEN1. But others did, especially those responsible for key stages of volatile production. Suggesting that STAY-GREEN1 influences the activity of genes involved in volatile compound production.
Chromoplasts
Lastly the researchers analysed the chloroplast themselves. They noticed that when the fruits ripened, those chloroplasts in plants without STAY-GREEN1 transitioned faster into chromoplasts, orange and red pigment producing organelles. The authors say that it is likely this faster transition that contribute to the higher volatile levels in those STAY-GREEN1 free tomatoes.
The question that remains after all this talk about how tomatoes with a richer volatile profile taste better, is if those STAY-GREEN1 free tomatoes actually taste better that the tomatoes with STAY-GREEN1. Unfortunately, the researchers do not mention this. Likely because strict regulations about eating your altered tomatoes before rigorous safety testing.
Literature
Jae-In Chun, Ga-Hae Han, Seong-Yeop Kim, Seong-Min Kim, Gab-Jung Kim, Bokyeong Kim, Jae Kwang Kim, Jwa Yeong Cho, Ho-Youn Kim, Jin-Ho Kang, Mutation of STAY-GREEN 1 in tomato increases volatile organic compounds during fruit ripening, Plant and Cell Physiology, 2026;, pcag018, https://doi.org/10.1093/pcp/pcag018
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