Maria Eugenia Zanetti - An LBD transcription factor acts downstream of ARF2 to control nodulation and root architecture

Abstract

Legume plants develop two types of root post-embryonic organs, lateral roots and symbiotic nodules, using shared regulatory components. The module composed by the microRNA390, the Trans-Acting SIRNA3 (TAS3) RNA and the Auxin Response Factors (ARF)2, ARF3, and ARF4 (miR390/TAS3/ARFs) mediates the control of both lateral roots and symbiotic nodules in legumes. Using a transcriptomic approach we have identified a member of the Lateral Organ Boundaries Domain (LBD) family of transcription factors in Medicago truncatula, designated MtLBD17/29a, which is regulated by the miR390/TAS3/ARFs module. ChIP-PCR experiments evidenced that MtARF2 binds to an Auxin Response Element present in the MtLBD17/29a promoter. MtLBD17/29a is expressed in root meristems, lateral root primordia, and noninfected cells of symbiotic nodules. Knockdown of MtLBD17/29a reduced the length of primary and lateral roots and enhanced lateral root formation, whereas overexpression of MtLBD17/29a produced the opposite phenotype. Interestingly, both knockdown and overexpression of MtLBD17/29a reduced nodule number and infection events and impaired the induction of the symbiotic genes Nodulation Signaling Pathway (NSP) 1 and 2. Our results demonstrate that MtLBD17/29a is regulated by the miR390/TAS3/ARFs module and a direct target of MtARF2, revealing a new lateral root regulatory hub recruited by legumes to act in the root nodule symbiotic program.

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Les 9, 10 et 11 septembre prochain la FRAIB reçoit 2 chercheurs argentins : Maria Eugenia Zanetti et Flavio Blanco dans le cadre de l'IRP franco-argentine « LOCOSYM ». Maria Eugenia Zanetti a obtenu son doctorat à l'université nationale de Mar del Plata (Argentine) en 2002. Elle a ensuite rejoint le laboratoire de Julia Bailey-Serres à l'université de Californie Riverside, en tant que chercheuse postdoctorale, où elle a mené des recherches fondamentales sur la purification par affinité des « translatomes » à partir de types de cellules spécifiques chez les plantes.

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