Cytokinin biosynthesis genes expressed during nodule organogenesis are directly regulated by the KNOX3 protein in Medicago truncatula.

Mahboobeh Azarakhsh,Lyudmila A Lutova,Andrey M Rumyantsev,Maria A Lebedeva,Francisco Martinez-Abarca

doi:10.1371/journal.pone.0232352

Mahboobeh Azarakhsh, Lyudmila A Lutova + Show 3 more

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https://doi.org/10.1371/journal.pone.0232352

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Journal: PloS one	Publication Date: Apr 30, 2020
Citations: 17	License type: CC BY 4.0

Affiliation: St Petersburg University, Kosar University of Bojnord

Abstract

Cytokinin is an important regulator of symbiotic nodule development. Recently, KNOTTED1-LIKE HOMEOBOX 3 transcription factor (TF) was shown to regulate symbiotic nodule development possibly via the activation of cytokinin biosynthesis genes. However, the direct interaction between the KNOX3 TF and its target genes has not been investigated up to date. Here, using EMSA analysis and SPR-based assay, we found that MtKNOX3 homeodomain directly binds to the regulatory sequences of the MtLOG1, MtLOG2, and MtIPT3 genes involved in nodulation in Medicago truncatula. Moreover, we showed that MtLOG2 and MtIPT3 expression patterns partially overlap with MtKNOX3 expression in developing nodules as it was shown by promoter:GUS analysis. Our data suggest that MtKNOX3 TF may directly activate the MtLOG1, MtLOG2, and MtIPT3 genes during nodulation thereby increasing cytokinin biosynthesis in developing nodules.

Highlights

KNOX (KNOTTED-like homeobox) homeodomain transcription factors (TFs) are important regulators of plant development
Based on this observation we proposed that MtKNOX3 could be responsible for the activation of cytokinin biosynthesis genes MtLOG2 and MtIPT3 during nodulation
To prove that MtLOG2 and MtIPT3 can be the targets of KNOX3 TF we first checked if these genes coexpress with the MtKNOX3 gene in nodules

Summary

Introduction

KNOX (KNOTTED-like homeobox) homeodomain transcription factors (TFs) are important regulators of plant development. There are two classes of KNOX genes, class I and class II [1]. Class I KNOX TFs regulate shoot apical meristem (SAM) development and maintenance, and the modulation of their expression patterns in SAM is associated with leaf shape diversity. The role of class II KNOX TFs is less understood. Class II KNOX genes are broadly expressed in differentiating tissues and mature organs [2].

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