Evolution and roles of cytokinin genes in angiosperms 1: Do ancient IPTs play housekeeping while non-ancient IPTs play regulatory roles?

Xiaojing Wang; Shanshan Lin; Decai Liu; Lijun Gan; Richard McAvoy; Jing Ding; Yi Li

doi:10.1038/s41438-019-0211-x

Evolution and roles of cytokinin genes in angiosperms 1: Do ancient IPTs play housekeeping while non-ancient IPTs play regulatory roles?

Hortic Res. 2020 Mar 1:7:28. doi: 10.1038/s41438-019-0211-x. eCollection 2020.

Authors

Xiaojing Wang^#¹, Shanshan Lin^#¹, Decai Liu¹, Lijun Gan², Richard McAvoy³, Jing Ding¹, Yi Li^{1

3}

Affiliations

¹ 1State Key Laboratory of Crop Genetics and Germplasm Enhancement and the College of Horticulture, Nanjing Agricultural University, Nanjing, P. R. China.
² 2College of Life Sciences, Nanjing Agricultural University, Nanjing, P. R. China.
³ 3Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT 06269 USA.

^# Contributed equally.

Abstract

Isopentenyltransferase (IPT) genes, including those encoding ATP/ADP-IPTs and tRNA-IPTs, control the rate-limiting steps of the biosynthesis of N ⁶-(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 10.1038/s41438-020-0246-z.

Keywords: Evolution; Plant evolution.