Expression Analysis of PIN Genes in Root Tips and Nodules of Medicago truncatula.

Izabela Sańko-Sawczenko,Barbara Łotocka,Weronika Czarnocka

doi:10.3390/ijms17081197

Izabela Sańko-Sawczenko, Barbara Łotocka + Show 1 more

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https://doi.org/10.3390/ijms17081197

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Abstract

Polar auxin transport is dependent on the family of PIN-formed proteins (PINs), which are membrane transporters of anionic indole-3-acetic acid (IAA−). It is assumed that polar auxin transport may be essential in the development and meristematic activity maintenance of Medicago truncatula (M. truncatula) root nodules. However, little is known about the involvement of specific PIN proteins in M. truncatula nodulation. Using real-time quantitative PCR, we analyzed the expression patterns of all previously identified MtPIN genes and compared them between root nodules and root tips of M. truncatula. Our results demonstrated significant differences in the expression level of all 11 genes (MtPIN1–MtPIN11) between examined organs. Interestingly, MtPIN9 was the only PIN gene with higher expression level in root nodules compared to root tips. This result is the first indication of PIN9 transporter potential involvement in M. truncatula nodulation. Moreover, relatively high expression level in root nodules was attributed to MtPINs encoding orthologs of Arabidopsis thaliana PIN5 subclade. PIN proteins from this subclade have been found to localize in the endoplasmic reticulum, which may indicate that the development and meristematic activity maintenance of M. truncatula root nodules is associated with intracellular homeostasis of auxins level and their metabolism in the endoplasmic reticulum.

Highlights

Nitrogen is the primary and most important nutrient for plants, since it is an element for amino acids and nucleobases biosynthesis
To perform a detailed expression analysis of PIN genes in M. truncatula root tips and nodules, we employed the real-time quantitative PCR technique
In order to unambiguously identify the phylogenetic relationship between M. truncatula and A. thaliana orthologs, we performed a Basic Local Alignment Search Tool (BLAST) alignment of each MtPIN’s coding DNA sequence (CDS) and full protein sequence with the A. thaliana nucleotide or protein database, respectively

Summary

Introduction

Nitrogen is the primary and most important nutrient for plants, since it is an element for amino acids and nucleobases biosynthesis. Plant species from the Fabaceae family have evolved an ability of establishing symbiosis with nitrogen-fixing bacteria, collectively called rhizobia, which allows them to exploit atmospheric nitrogen sources This type of symbiosis is an effective evolutionary adaptation, which enables fabaceans to accumulate high levels of nitrogen in their tissues [1]. The host plant needs to ensure a microaerobic environment in the infected cells This is indispensable for the proper activity of nitrogenase, an oxygen-labile enzyme directly responsible for the dinitrogen fixation. Such an environment is created by the presence of symbiotic leghemoglobins, hemoproteins present in root nodules. Since ammonium is toxic to plant cells, it is immediately assimilated by presumably three interdependent metabolic pathways engaging asparagine synthetase, glutamine synthetase or glutamate dehydrogenase [8]

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