Silencing of Putative Cytokinin Receptor Histidine Kinase1 Inhibits Both Inception and Differentiation of Root Nodules in Arachis hypogaea

Kundu, Anindya ; DasGupta, Maitrayee (2018) Silencing of Putative Cytokinin Receptor Histidine Kinase1 Inhibits Both Inception and Differentiation of Root Nodules in Arachis hypogaea Molecular Plant-Microbe Interactions, 31 (2). pp. 187-199. ISSN 0894-0282

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Official URL: http://doi.org/10.1094/MPMI-06-17-0144-R

Related URL: http://dx.doi.org/10.1094/MPMI-06-17-0144-R

Abstract

Rhizobia–legume interaction activates the SYM pathway that recruits cytokinin signaling for induction of nodule primordia in the cortex. In Arachis hypogaea, bradyrhizobia invade through natural cracks developed in the lateral root base and are directly endocytosed in the cortical cells to generate the nodule primordia. To unravel the role of cytokinin signaling in A. hypogaea, RNA-interference (RNAi) of cytokinin receptor histidine-kinase1 (AhHK1) was done. AhHK1-RNAi downregulated the expression of type-A response regulators such as AhRR5 and AhRR3 along with several symbiotic genes, indicating that both cytokinin signaling and the SYM pathway were affected. Accordingly, there was a drastic downregulation of nodulation in AhHK1-RNAi roots and the nodules that developed were ineffective. These nodules were densely packed, with infected cells having a higher nucleo-cytoplasmic ratio and distinctively high mitotic index, where the rod-shaped rhizobia failed to differentiate into bacteroids within spherical symbiosomes. In accordance with the proliferating state, expression of a mitotic-cyclin AhCycB2.1 was higher in AhHK1-RNAi nodules, whereas expression of a retinoblastoma-related (AhRBR) nodule that restrains proliferation was lower. Also, higher expression of the meristem maintenance factor WUSCHEL-RELATED HOMEOBOX5 correlated with the undifferentiated state of AhHK1-RNAi nodules. Our results suggest that AhHK1-mediated cytokinin signaling is important for both inception and differentiation during nodule development in A. hypogaea.

Item Type:Article
Source:Copyright of this article belongs to The American Phytopathological Society.
ID Code:123625
Deposited On:10 Oct 2021 08:07
Last Modified:10 Oct 2021 08:07

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