Abstract
MOB1 protein is a core component of the Hippo signaling pathway in animals where it is involved in controlling tissue growth and tumor suppression. Plant MOB1 proteins display high sequence homology to animal MOB1 proteins, but little is known regarding their role in plant growth and development. Herein we report the critical roles of Arabidopsis MOB1 (AtMOB1A) in auxin-mediated development in Arabidopsis. We found that loss-of-function mutations in AtMOB1A completely eliminated the formation of cotyledons when combined with mutations in PINOID (PID), which encodes a Ser/Thr protein kinase that participates in auxin signaling and transport. We showed that atmob1a was fully rescued by its Drosophila counterpart, suggesting functional conservation. The atmob1a pid double mutants phenocopied several well-characterized mutant combinations that are defective in auxin biosynthesis or transport. Moreover, we demonstrated that atmob1a greatly enhanced several other known auxin mutants, suggesting that AtMOB1A plays a key role in auxin-mediated plant development. The atmob1a single mutant displayed defects in early embryogenesis and had shorter root and smaller flowers than wild type plants. AtMOB1A is uniformly expressed in embryos and suspensor cells during embryogenesis, consistent with its role in embryo development. AtMOB1A protein is localized to nucleus, cytoplasm, and associated to plasma membrane, suggesting that it plays roles in these subcellular localizations. Furthermore, we showed that disruption of AtMOB1A led to a reduced sensitivity to exogenous auxin. Our results demonstrated that AtMOB1A plays an important role in Arabidopsis development by promoting auxin signaling.
Highlights
In recent years, the Hippo signaling pathway has emerged as a very important pathway for animal development [1]
MOB1 protein is a key component of the Hippo signaling pathway in animals, and it plays critical roles in organ size control
We showed that AtMOB1A, which is highly homologous to animal MOB1 proteins, plays an important role in plant organogenesis
Summary
The Hippo signaling pathway has emerged as a very important pathway for animal development [1] This highly conserved pathway was initially identified in Drosophila as a key pathway controlling organ size, and later was shown to play a role in controlling cell fate and pattern formation in mammals [2,3,4,5]. Hippo signaling controls patterning and differentiation of airway epithelial progenitors, mammary gland differentiation, intestinal fate, cardiovascular, liver, pancreas, central nervous system, and lymphocyte development [2]. It regulates stem cell self-renewal and cell polarity in animals [2,13,14]. Very little is known regarding how the hypothesized Hippo pathway may regulate plant growth and development
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