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Plant function and evolutionary biology
REVIEW

Cell differentiation in nitrogen-fixing nodules hosting symbiosomes

Anna V. Tsyganova A , Anna B. Kitaeva A and Viktor E. Tsyganov A B
+ Author Affiliations
- Author Affiliations

A All-Russia Research Institute for Agricultural Microbiology, Laboratory of Molecular and Cellular Biology, Podbelsky chaussee 3, 196608, Pushkin 8, Saint-Petersburg, Russia.

B Corresponding author. Email: tsyganov@arriam.spb.ru

This paper originates from a presentation at the Fourth International Symposium on Plant Signaling and Behavior, Komarov Botanical Institute RAS/Russian Science Foundation, Saint Petersburg, Russia, 1923 June 2016.

Functional Plant Biology 45(2) 47-57 https://doi.org/10.1071/FP16377
Submitted: 29 October 2016  Accepted: 25 January 2017   Published: 7 March 2017

Abstract

The nitrogen-fixing nodule is a unique ecological niche for rhizobia, where microaerobic conditions support functioning of the main enzyme of nitrogen fixation, nitrogenase, which is highly sensitive to oxygen. To accommodate bacteria in a symbiotic nodule, the specialised infected cells increase in size owing to endoreduplication and are able to shelter thousands of bacteria. Bacteria are isolated from the cytoplasm of the plant cell by a membrane-bound organelle-like structure termed the symbiosome. It is enclosed by a symbiosome membrane, mainly of plant origin but with some inclusion of bacterial proteins. Within the symbiosome, bacterial cells differentiate into bacteroids a form that is specialised for nitrogen fixation. In this review, we briefly summarise recent advances in studies of differentiation both of symbiosomes and of the infected cells that accommodate them. We will consider the role of CCS52A, DNA topoisomerase VI, tubulin cytoskeleton rearrangements in differentiation of infected cells, the fate of the vacuole, and the distribution of symbiosomes in the infected cells. We will also consider differentiation of symbiosomes, paying attention to the role of NCR peptides, vesicular transport to symbiosomes, and mutant analysis of symbiosome development in model and crop legumes. Finally, we conclude that mechanisms involved in redistribution organelles, including the symbiosomes, clearly merit much more attention.

Additional keywords: cytoskeleton, nodulation, organelles, plant–microbe interactions, Rhizobium spp., symbiosis.


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