IPT9, a cis-zeatin cytokinin biosynthesis gene, promotes root growth

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Authors

ANTONIADI Ioanna MATEO-BONMATÍ Eduardo PERNISOVÁ Markéta BRUNONI Federica ANTONIADI Mariana VILLALONGA Mauricio Garcia-Atance AMENT Anita KARÁDY Michal TURNBULL Colin DOLEŽAL Karel PĚNČÍK Aleš LJUNG Karin NOVÁK Ondřej

Year of publication 2022
Type Article in Periodical
Magazine / Source Frontiers in Plant Science
MU Faculty or unit

Faculty of Science

Citation
Web https://www.frontiersin.org/articles/10.3389/fpls.2022.932008/full
Doi http://dx.doi.org/10.3389/fpls.2022.932008
Keywords cytokinin; auxin; plant hormones; root growth; metabolism
Description Cytokinin and auxin are plant hormones that coordinate many aspects of plant development. Their interactions in plant underground growth are well established, occurring at the levels of metabolism, signaling, and transport. Unlike many plant hormone classes, cytokinins are represented by more than one active molecule. Multiple mutant lines, blocking specific parts of cytokinin biosynthetic pathways, have enabled research in plants with deficiencies in specific cytokinin-types. While most of these mutants have confirmed the impeding e??ect of cytokinin on root growth, the ipt29 double mutant instead surprisingly exhibits reduced primary root length compared to the wild type. This mutant is impaired in cis-zeatin (cZ) production, a cytokinin-type that had been considered inactive in the past. Here we have further investigated the intriguing ipt29 root phenotype, opposite to known cytokinin functions, and the (bio)activity of cZ. Our data suggest that despite the ipt29 short-root phenotype, cZ application has a negative impact on primary root growth and can activate a cytokinin response in the stele. Grafting experiments revealed that the root phenotype of ipt29 dependsmainly on local signaling which does not relate directly to cytokinin levels. Notably, ipt29 displayed increased auxin levels in the root tissue. Moreover, analyses of the di??erential contributions of ipt2 and ipt9 to the ipt29 short-root phenotype demonstrated that, despite its deficiency on cZ levels, ipt2 does not show any root phenotype or auxin homeostasis variation, while ipt9 mutants were indistinguishable from ipt29. We conclude that IPT9 functions may go beyond cZ biosynthesis, directly or indirectly, implicating e??ects on auxin homeostasis and therefore influencing plant growth.
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