Nod-Factor Signaling in Legume-Rhizobial Symbiosis

Abstract

Leguminous plants or Legumes, family Fabaceae are known to form symbioses with extremely broad range of beneficial soil microorganisms "SM , representing examples of almost all plant-microbe mutualistic systems. One of the most ecologically important and well-studied legume beneficial symbioses is root nodule RN symbiosis symbiotic association with nitrogen-fixing bacteria . Compared with other interactions of legumes with "SM, RN symbioses demonstrate high level of genetic and metabolic integrity, which implies, inter alia, highly specific mutual recognition of partners. In this chapter, we describe the mechanisms of plant-microbe recognition during initial steps of RN symbiosis using the interaction of model legumes -pea Pisum sativum L. , barrel medic Medicago truncatula Gaertn. and Lotus japonicus Regel. K. Larsen -with rhizobia as an example. We paid particular attention to symbiotic system of P. sativum since pea, besides its importance as a model object of genetics, is also a valuable crop plant. Hence, in conclusion, we discuss the potential to use obtained knowledge for optimizing the broad spectrum of plant adaptive functions and to improve the sustainability of legume crop production.Keywords: legume-rhizobial symbiosis, Nod factor, plant signaling, genetic control . IntroductionPlants are attached immobile organisms and thus have to adapt to their environment in order to survive and reproduce successfully. Usually, plants experience multiple simultaneous © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.impacts from different sources, so they developed complex signaling pathways to effectively detect these impacts and adequately respond to them [ ]. Various microorganisms, which are constantly present in the environment, form one of the major factors affecting the life cycle of plants [ , ]. "lthough many plant-associated microbes are pathogens that impair plant growth and reproduction, there are also a lot of beneficial mutualistic microorganisms able to provide plants with nutrition and additional defense mechanisms. Cooperation with such microorganisms constitutes the universal and highly effective strategy of plants' ecological adaptation, so they tend to form long-lasting associations, which sometimes grow into highly integrated symbioses where one or both partners can develop novel features useful for their survival. Establishing of such symbiotic relationships involves the complicated developmental programs implemented under the joint control by plant and microbial partners and based on the cross-regulation of their genes.Leguminous plants or Legumes, family Fabaceae are known to form symbioses with extremely broad range of beneficial soil microorganisms "SM , representing examples of almost all plant-microbe mutualistic systems. One of the mos...

Signaling in Legume–Rhizobia Symbiosis

“…Among the latter, R. leguminosarum strain TOM, which has a nodX gene, encoding a specific O-acetyltransferase modifying the reducing end of the sugar backbone in NFs, can be mentioned. This feature of the pea plant is controlled by a specific recessive allele of Sym2 gene usually referred to as the "Afghan allele" (Sym2 A ) [10]. Although this was the first pea symbiotic gene to be discovered, its molecular function is still elusive.…”

“…To date, the legume-rhizobia symbiosis is well-characterized, and the underlying mechanisms of genome regulation represent the most comprehensively elaborated aspect of this phenomenon [5][6][7][8][9][10]. Therefore, the individual steps of the corresponding regulatory pathways were addressed in much detail [11][12][13][14].…”

Microbiota do solo na tolerância de doenças em plantas: Uma revisão

“…A infecção das bactérias ocorre por meio de atração quimiostática, onde a raiz secreta flavonóides e betaínas que direcionam a bactéria à raiz, e nesta encontram-se lecitinas receptoras produzidas nos pelos radiculares (Figura 2), (Sergeevich, et al, 2015).…”

“…Legenda: F: Flavanóides; NF: Fatores de nodulação excretados pela bactéria; IT: Fio de infecção que promove a diferenciação do nódulo; B: Bacterióide. Fonte: Sergeevich et al (2015).…”

“…Durante a atração da bactéria pela raiz, ocorre a transcrição dos genes Nod, e ao entrar em contato com os pelos radiculares são liberados os fatores de nodulação que induzem o enrolamento, em sequência ocorre a formação de primórdio nodular, com posterior divisão no citoplasma até o nódulo tornar-se maturo, o nódulo apresenta bacterióide que facilita as interações com a planta (Sergeevich, et al, 2015).…”