Characterizing a Novel Connection Between the Plant Hormones Cytokinin and Jasmonic Acid in Control of Maize Leaf Growth.

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2018-08
Authors
Uyehara, Aimee N.
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Tropical Plant & Soil Sciences
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Plant growth is the accumulation of biomass over time and is due the combined effects of cell division and cell expansion. Understanding the molecular basis of plant growth in the context of the growthbdefense tradeoff is important for agricultural sciences, and using a simple model to study growth enables this type of research. In Zea&mays&L. (maize), growth is spatially separated into three distinct growth zones making the maize leaf base a useful model for investigating growth on multiple scales. Mutants that affect maize leaf size are useful as an entry into the molecular networks guiding growth. The semibdominant maize mutant, Hairy&Sheath&Frayed&(Hsf1)&is a CK hypersignaler with reduced leaf size, fewer dividing cells, and increased levels of the hormone jasmonic acid (JA) in the leaf growth zone. To determine if increased JA content in&Hsf1&contributes to its reduced leaf growth, the effects of JA on normal maize leaf growth were characterized. Our results showed that JA treatment dramatically reduced maize leaf size by reducing growth rate. Reduced JA content in the JA deficient opr7,&opr8 mutant led to increased leaf size mediated by an increased growth rate. Analysis of epidermal cell counts suggested that JA reduces cell proliferation rate, since cell size and density were not affected. Exogenous JA treatments of Hsf1 indicated the mutant has a reduced response to JA. These data help explain the basis of growth reduction in Hsf1&and set the foundation for further studies to uncover the players that mediate a novel interaction between CK and JA.
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Maize, Jasmonic Acid, Cytokinin, Hsf1, Leaf Growth
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