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Article|01 Mar 2020|OPEN
Evolution and roles of cytokinin genes in angiosperms 1: Do ancient IPTs play housekeeping while non-ancient IPTs play regulatory roles?
Xiaojing Wang1, Shanshan Lin1, Decai Liu1, Lijun Gan2, Richard McAvoy3, Jing Ding1, & Yi Li1,3,
1State Key Laboratory of Crop Genetics and Germplasm Enhancement and the College of Horticulture, Nanjing Agricultural University, Nanjing, P. R. China
2College of Life Sciences, Nanjing Agricultural University, Nanjing, P. R. China
3Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT 06269, USA

Horticulture Research 7,
Article number: 28 (2020)
doi: 10.1038/hortres.2020.28
Views: 632

Received: 01 Jun 2019
Revised: 04 Jun 2019
Accepted: 05 Jun 2019
Published online: 01 Mar 2020

Abstract

Isopentenyltransferase (IPT) genes, including those encoding ATP/ADP-IPTs and tRNA-IPTs, control the rate-limiting steps of the biosynthesis of N6-(Δ2-isopentenyl)adenine (iP)-type and trans-zeatin (tZ)-type cytokinins and cis-zeatin (cZ)-type cytokinins, respectively. However, the evolution and roles of these IPTs in angiosperms are not well understood. Here, we report comprehensive analyses of the origins, evolution, expression patterns, and possible roles of ATP/ADP-IPTs and tRNA-IPTs in angiosperms. We found that Class I and II tRNA-IPTs likely coexisted in the last common ancestor of eukaryotes, while ATP/ADP-IPTs likely originated from a Class II tRNA-IPT before the divergence of angiosperms. tRNA-IPTs are conservatively retained as 2–3 copies, but ATP/ADP-IPTs exhibit considerable expansion and diversification. Additionally, tRNA-IPTs are constitutively expressed throughout the plant, whereas the expression of ATP/ADP-IPTs is tissue-specific and rapidly downregulated by abiotic stresses. Furthermore, previous studies and our present study indicate that ATP/ADP-IPTs and their products, iPs/tZs, may regulate responses to environmental stresses and organ development in angiosperms. We therefore hypothesize that tRNA-IPTs and the associated cZs play a housekeeping role, whereas ATP/ADP-IPTs and the associated iP/tZ-type cytokinins play regulatory roles in organ development and stress responses in angiosperms, which echoes the conclusions and hypothesis presented in the accompanying study by Wang, X. et al Evolution and roles of cytokinin genes in angiosperms 2: Do ancient CKXs play housekeeping roles while non-ancient CKXs play regulatory roles? Hortic Res https://doi.org/10.1038/s41438-020-0246-z.