The Role of OsYUCCA2 in Auxin Synthesis and Promotion of Rice Growth and Development
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The Role of OsYUCCA2 in Auxin Synthesis and Promotion of Rice Growth and Development X. L. Hana, *, F. Y. Zhaoa, **, Z. L. Wangb, X. Chea, and G. C. Cuia aCollege
bShandong
of Life Sciences, Shandong University of Technology, Zibo, China Provincial Key Laboratory of Plant Stress Research, College of Life Science, Shandong Normal University, Jinan, China *e-mail: [email protected] **e-mail: [email protected] Received March 17, 2020; revised May 21, 2020; accepted May 22, 2020
Abstract—YUCCA (YUC) proteins are essential for auxin production and play critical roles in plant growth and development. Many of the fourteen rice OsYUCs identified to date have been characterized, but the functions and expression patterns of OsYUC2 remain unclear. In this study, transgenic rice seedlings (Oryza sativa L. ‘Nipponbare’) overexpressing GUS-tagged OsYUC2 under the control of the ubiquitin promoter or the native OsYUC2 promoter were used to investigate OsYUC2 expression and function. OsYUC2 distribution was restricted to rapidly dividing cells in callus, vegetative, and reproductive tissues. OsYUC2 overexpression promoted plant growth, leading to proliferation of embryonic, adventitious, and lateral roots, and increases in shoot height and grain weight. OsYUC2 localization correlated with auxin localization, and auxin content analysis showed that IAA levels were higher in OsYUC2 transgenic rice than in the wild-type. Furthermore, exogenous addition of 3-indolebutyric acid (IBA, an analogue of IAA) in wild-type plants produced growth phenotypes similar to those of OsYUC2 transgenic rice seedlings. Our results indicate that OsYUC2 has distinct expression patterns and regulates major growth and developmental processes in rice. Keywords: Oryza sativa, OsYUC2, auxin, rice growth DOI: 10.1134/S1021443720060072
INTRODUCTION Auxin is a critical regulator of many plant growth and development processes including cell division, cell differentiation, shoot and root growth, lateral root formation, and pathogen and abiotic stress responses [1]. Auxin in plant signaling functions during growth and development are regulated by local biosynthesis, transport, and perception by receptors. It is thus critical that spatial and temporal homeostasis of auxin distribution in plants are tightly controlled, and this is achieved by the control of auxin biosynthesis by several genes [2, 3]. The main plant auxin, indole-3-acetic acid (IAA), can be synthesized by tryptophan-dependent and tryptophan-independent routes [2, 4]. Although IAA can be produced by IAA conjugates via the tryptophan-independent route, the tryptophan-dependent route is considered to be the predominant IAA pathway, with tryptophan as the major precursor [2]. The tryptophandependent route in plants can occur via several pathways, including the indole-3-pyruvic acid (IPA), indole-3-acetamide (IAM), tryptamine (TAM), and Abbreviations: AR—adventitious root; ER—embryonic root; GUS—β-glucuronidase; G3 and G4—OsYUC2 transgenic rice seedlings; IBA—Indole-3-butytric acid; LR—latera
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