AUTHOR=Lomin Sergey N. , Myakushina Yulia A. , Kolachevskaya Oksana O. , Getman Irina A. , Savelieva Ekaterina M. , Arkhipov Dmitry V. , Deigraf Svetlana V. , Romanov Georgy A. 

TITLE=Global View on the Cytokinin Regulatory System in Potato

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.613624

DOI=10.3389/fpls.2020.613624

ISSN=1664-462X

ABSTRACT=<p>Cytokinins (CKs) were earlier shown to promote potato tuberization. Our study aimed to identify and characterize CK-related genes which constitute CK regulatory system in the core potato (<italic>Solanum tuberosum</italic>) genome. For that, CK-related genes were retrieved from the sequenced genome of the <italic>S. tuberosum</italic> doubled monoploid (DM) Phureja group, classified and compared with Arabidopsis orthologs. Analysis of selected gene expression was performed with a transcriptome database for the <italic>S. tuberosum</italic> heterozygous diploid line RH89-039-16. Genes responsible for CK signaling, biosynthesis, transport, and metabolism were categorized in an organ-specific fashion. According to this database, CK receptors StHK2/3 predominate in leaves and flowers, StHK4 in roots. Among phosphotransmitters, StHP1a expression largely predominates. Surprisingly, two pseudo-phosphotransmitters intended to suppress CK effects are hardly expressed in studied organs. Among B-type <italic>RR</italic> genes, <italic>StRR1b</italic>, <italic>StRR11</italic>, and <italic>StRR18a</italic> are actively expressed, with <italic>StRR1b</italic> expressing most uniformly in all organs and <italic>StRR11</italic> exhibiting the highest expression in roots. By cluster analysis four types of prevailing CK-signaling chains were identified in (1) leaves and flowers, StHK2/3→<italic>S</italic><italic>t</italic><italic>H</italic><italic>P</italic>1<italic>a</italic>→StRR1b/+; (2) shoot apical meristems, stolons, and mature tubers, StHK2/4→<italic>S</italic><italic>t</italic><italic>H</italic><italic>P</italic>1<italic>a</italic>→StRR1b/+; (3) stems and young tubers, StHK2/4→<italic>S</italic><italic>t</italic><italic>H</italic><italic>P</italic>1<italic>a</italic>→StRR1b/11/18a; and (4) roots and tuber sprouts, StHK4→<italic>S</italic><italic>t</italic><italic>H</italic><italic>P</italic>1<italic>a</italic>→StRR11/18a. CK synthesis genes <italic>StIPT3</italic>/<italic>5</italic> and <italic>StCYP735A</italic> are expressed mainly in roots followed by tuber sprouts, but rather weakly in stolons and tubers. By contrast, CK-activation genes <italic>StLOGs</italic> are active in stolons, and <italic>StLOG3b</italic> expression is even stolon-confined. Apparently, the main CK effects on tuber initiation are realized via activity of <italic>StLOG1/3a/3b/7c/8a</italic> genes in stolons. Current advances and future directions in potato research are discussed.</p>