Park Sang-Il, Park Hye-Lin, Bhoo Seong-Hee, Lee Sang-Won, Cho Man-Ho
Department of Genetics and Biotechnology, Kyung Hee University, Yongin 17104, Korea.
Plants (Basel). 2021 Sep 30;10(10):2064. doi: 10.3390/plants10102064.
Chalcone isomerase (CHI) is a key enzyme in flavonoid biosynthesis. In plants, CHIs occur in multigene families, and they are divided into four types, types I-IV. Type I and II CHIs are bona fide CHIs with CHI activity, and type III and IV CHIs are non-catalytic members with different functions. Rice contains seven CHI family genes (s). Molecular analysis suggested that OsCHI3 is a type I CHI, and the other OsCHIs were classified into types III and IV. To elucidate their biochemical functions, OsCHI1, OsCHI3, OsCHI6, and OsCHI7 were expressed in , and the recombinant OsCHI proteins were purified. An activity assay of recombinant OsCHIs showed that OsCHI3 catalyzed the isomerization of naringenin chalcone and isoliquiritigenin, whereas the other recombinant OsCHIs had no CHI activity. OsCHI3 also exhibited a strong preference to naringenin chalcone compared to isoliquiritigenin, which agrees well with the catalytic properties of type I CHIs. These results ascertain OsCHI3 to be a bona fide CHI in rice. and the other s were expressed constitutively throughout the rice growth period and different tissues. expression was induced immediately in response to ultra-violet (UV) stress, suggesting its involvement in the biosynthesis of sakuranetin, a flavonoid phytoalexin in rice.
查尔酮异构酶（CHI）是类黄酮生物合成中的关键酶。在植物中，CHI存在于多基因家族中，分为I - IV型。I型和II型CHI是具有CHI活性的真正的CHI，而III型和IV型CHI是具有不同功能的非催化成员。水稻含有7个CHI家族基因。分子分析表明，OsCHI3是I型CHI，其他OsCHI被归类为III型和IV型。为了阐明它们的生化功能，在[具体表达系统未给出]中表达了OsCHI1、OsCHI3、OsCHI6和OsCHI7，并纯化了重组OsCHI蛋白。重组OsCHI的活性测定表明，OsCHI3催化柚皮素查尔酮和异甘草素的异构化，而其他重组OsCHI没有CHI活性。与异甘草素相比，OsCHI3对柚皮素查尔酮也表现出强烈的偏好，这与I型CHI的催化特性非常吻合。这些结果确定OsCHI3是水稻中真正的CHI。并且其他[未明确的基因相关内容]在水稻整个生长周期和不同组织中组成型表达。[OsCHI6]的表达在紫外线（UV）胁迫下立即被诱导，表明它参与了水稻中类黄酮植保素樱花素的生物合成。
