Research press release


Nature Communications

Genetics: The source of sour citrus taste



今回、Ronald Koesたちの研究グループは、柑橘類(レモン、オレンジ、ザボン、ライム)の酸っぱい品種と甘い品種を比較した。その結果、酸っぱい品種では、注入プロセスを増進させて、液胞中の水素イオンの濃度を上昇させる輸送体タンパク質をコードする2種類の遺伝子(CitPH1とCitPH5)が発現していることが分かった。一方、甘い「無酸」種では、この2種類の遺伝子の発現は低かった。なお、この輸送体タンパク質は、Koesたちが先行研究でペチュニアの紫の花色の基盤となっている輸送体タンパク質として同定したものと同種のものだった。


The genes associated with the sour taste of citrus fruits are identified in a paper published in Nature Communications this week.

The sourness of a fruit depends on the acidity of the vacuole (a membrane-bound organelle found in plant cells). In most plant cells, the vacuole is moderately acidic because hydrogen ions are pumped into it. In the juice-producing cells of certain fruits, this pumping process is increased leading to intense acidity in the vacuole. However, it was previously unclear how this was achieved.

Ronald Koes and colleagues compared sweet and sour tasting varieties of citrus fruits including lemons, oranges, pummelos and limes. The authors found that sour varieties express two genes called CitPH1 and CitPH5, which encode transporter proteins that amplify the pumping process, increasing the concentration of hydrogen ions in the vacuole. Expression of these two genes was reduced in sweet-tasting ‘acidless’ varieties of the fruits. This is also the same type of transporter the authors previously found to underlie the purple flower colour of petunias.

The authors conclude that the findings could help fruit breeders to select better tasting fruit more quickly. By testing the DNA of young saplings, breeders may be able to predict the sourness of the fruit, rather than having to wait for the fruit tree to mature.

doi: 10.1038/s41467-019-08516-3

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