vavilovВавиловский журнал генетики и селекцииVavilov Journal of Genetics and Breeding2500-3259Institute of Cytology and Genetics of Siberian Branch of the RAS10.18699/VJ18.328vavilov-1359Research ArticleГЕНЕТИКА И СЕЛЕКЦИЯ КАРТОФЕЛЯPOTATO GENETICS AND BREEDINGРЕГУЛЯЦИЯ БИОСИНТЕЗА СТЕРОИДНЫХ ГЛИКОАЛКАЛОИДОВ КАРТОФЕЛЯTHE BIOSYNTHESIS REGULATION OF POTATO STEROIDAL GLYCOALKALOIDSИвановаК. А.IvanovaK. A.

Новосибирск

Novosibirsk

ivanova@bionet.nsc.ruГерасимоваС. В.GerasimovaS. V.

Новосибирск

Novosibirsk

ХлесткинаЕ. К.KhlestkinaE. K.

Новосибирск

Novosibirsk

Федеральный исследовательский центр Институт цитологии и генетики Сибирского отделения Российской академии наукРоссияInstitute of Cytology and Genetics SB RASRussian Federation2018210320182212534Copyright © Иванова К.А., Герасимова С.В., Хлесткина Е.К., 20182018Иванова К.А., Герасимова С.В., Хлесткина Е.К.Ivanova K.A., Gerasimova S.V., Khlestkina E.K.This work is licensed under a Creative Commons Attribution 4.0 License.https://vavilov.elpub.ru/jour/article/view/1359

Стероидные гликоалкалоиды (СГА) картофеля составляют часть иммунитета растений. Некоторые их модифицированные формы токсичны для человека. В ходе доместикации картофеля происходил отбор растений с пониженным уровнем СГА. В настоящее время с появлением методов, при помощи которых возможно специфично влиять на регуляцию метаболических путей, появляется перспектива преодолеть нежелательную прямую взаимосвязь между устойчивостью картофеля к вре дителям и токсичностью его клубней. Однако для таких целенаправленных тонких изменений необходимы глубокие знания о регуляторной сети биосинтеза СГА картофеля. Цель обзора –  обобщить сведения об известных генах биосинтеза СГА у растений, суммировать данные об исследовании этих генов у картофеля, а также рассмотреть механизмы защитного токсического действия СГА против патогенов и вредителей. Биосинтез СГА идет по мевалонатному пути, который реализуется в цитозоле и состоит из трех этапов. Первые два этапа относятся к синтезу первичных метаболитов и приводят к циклоартанолу и холестерину соответственно. В биосинтез вовлечены 12 ферментов, половина из которых также участвует в биосинтезе фитостеринов, являющемся ответвлением первого этапа этого метаболического пути. В листьях картофеля при избытке фитостеринов синтез переключается на СГА, повышая их содержание. В клубнях при избытке предшественников СГА происходит вовлечение их в синтез ланостерола, что позволяет поддерживать стабильность уровня СГА в этой части растений. Значимость структурных генов, кодирующих ферменты первых двух этапов биосинтеза, не позволяет рассматривать их в качестве мишеней для нокаута с целью снижения уровня СГА. Однако информация о тканеспецифичных механизмах переключения между путями синтеза СГА и других соединений, имеющих общих с СГА предшественников, может быть использована для манипуляции с тканеспецифичным уровнем стероидных гликоалкалоидов. На третьем этапе (собственно синтез гликоалкалоидов из холестерина) участвуют около 20 ферментов. В геноме картофеля идентифицировано 14 соответствующих им генов, 8 из которых детально изучены при помощи методов обратной генетики. В качестве перспективных мишеней для снижения уровня СГА в клубнях могут рассматриваться гены, кодирующие ферменты PGA (относящиеся к подсемейству CYP72 цитохром-P450-зависимых монооксигеназ, катализирующие превращение гидрохолестерина в тригидрохолестерин) и SGT (СГА-гликозилтрансферазы, осуществляющие превращение соланидина в его токсичные гликозилированные производные – α-соланин и α-хаконин). Описаны цис-регуляторные элементы в промоторных областях некоторых генов биосинтеза гликоалкалоидов, включая элементы, ответственные за тканеспецифичную экспрессию. Накопленные сведения служат основой для создания генотипов картофеля с тканеспецифичной регуляцией СГА, в которых при сохранении высокого уровня СГА в листьях для защиты от патогенов и вредителей будет подавляться синтез токсических веществ в клубнях

Potato steroidal glycoalkaloids (SGAs) compose a part of plant immunity. Some of their modified variants are toxic to humans. In the course of potato domestication, plants with a lower SGA level were selected. The advent of approaches for manipulation with the regulation of metabolic pathways provides an opportunity to overcome the undesirable direct relationship between the potato resistance to pests and the toxicity of its tubers. However, for such a fine regulation, a deep knowledge of the regulatory network of potato SGA biosynthesis is required. The purpose of this review is to summarize the information on the known SGA biosynthesis genes in plants and the results of the investigation of these genes in potato, as well as to consider the mechanisms of the SGA protective toxic action against pathogens and pests. The SGA biosynthesis is realized via the cytosolic mevalonate pathway and consists of three stages. The first two stages are required for the synthesis of primary metabolites, and lead to cycloartanol and cholesterol, respectively. Twelve enzymes are involved in the biosynthesis, and the half of them are involved in the biosynthesis of phytosterols, which is a branch of the first stage of this metabolic pathway. In the potato leaves with an excess of phytosterols, the synthesis switches to SGAs, increasing the content of the latter. In tubers, with an excess of SGA precursors, they are involved in the synthesis of lanosterol, supporting in this way the stable level of SGA. The importance of structural genes encoding the enzymes of the first two stages of biosynthesis does not allow us to consider them as a target for knockout in order to reduce the level of SGAs. However, information about the tissue-specific mechanisms of switching between the pathways of synthesis of SGA and other compounds having common precursors with SGAs can be used to manipulate the tissue-specific level of steroidal glycoalkaloids. At the third stage (the synthesis of glycoalkaloids from cholesterol), about 20 enzymes participate. In the potato genome, 14 corresponding genes were identified, 8 of which were studied in detail using reverse genetics approaches. As a promising target for reducing SGA levels in tubers, the genes encoding PGA enzymes (belonging to the CYP72 subfamily cytochrome-P450-dependent monooxygenases catalyzing the conversion of hydrocholesterol to trihydrocholesterol) and SGT (SGA glycosyltransferases that catalyze the conversion of solanidine to its toxic glycosylated derivatives α-solanine and α-chaconine) are considered. Cis-regulatory elements in the promoter regions of some glycoalkaloid biosynthesis genes, including elements responsible for tissue-specific expression, are described. The accumulated information provides the base for creating potato genotypes with tissue-specific regulation of SGAs, in which high levels of SGAs in leaves will remain to protect against pathogens and pests and, at the same time, the synthesis of toxic substances in tubers will be suppressed

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The authors declare that there are no conflicts of interest present.