The innovation of the symbiosome has enhanced the evolutionary stability of nitrogen fixation in legumes

Nitrogen-fixing symbiosis is globally important in ecosystem functioning and agriculture, yet the evolutionary history of nodulation remains the focus of considerable debate. Recent evidence suggesting a single origin of nodulation followed by massive parallel evolutionary losses raises questions about why a few lineages in the N2-fixing clade retained nodulation and diversified as stable nodulators, while most did not. Within legumes, nodulation is restricted to the two most diverse subfamilies, Papilionoideae and Caesalpinioideae, which show stable retention of nodulation across their core clades. We characterize two nodule anatomy types across 128 species in 56 of the 152 genera of the legume subfamily Caesalpinioideae: fixation thread nodules (FTs), where nitrogen-fixing bacteroids are retained within the apoplast in modified infection threads, and symbiosomes, where rhizobia are symplastically internalized in the host cell cytoplasm within membrane-bound symbiosomes (SYMs). Using a robust phylogenomic tree based on 997 genes from 147 Caesalpinioideae genera, we show that losses of nodulation are more prevalent in lineages with FTs than those with SYMs. We propose that evolution of the symbiosome allows for a more intimate and enduring symbiosis through tighter compartmentalization of their rhizobial microsymbionts, resulting in greater evolutionary stability of nodulation across this species-rich pantropical legume clade

Diversity in native legumes of the Indian Thar Desert and a look into Socio-economic aspect

The arid and semi arid regions of Rajasthan are characterized by low precipitation, high and hot summer winds, high thermal load and saline tracts. More than 60% of the hot and arid regions of India are in the state of Rajasthan. This region harbors several nodulating native as well as exotic legumes and associated diverse rhizobia. Beside their role in soil fertility and sand stabilization, these legumes are sources of food, fodder, medicine, shelter and firewood for the local inhabitants

Endophytic bacterial diversity in root nodules of native legumes from Indian Thar Desert

Arid and semi arid regions of the Indian Thar Desert possess several nodulating native legumes important to the local inhabitants for food, fodder, shelter and medicines. These legumes are useful in dry land Cultivation and soil improvement for rain-fed crops in arid and semi arid areas, The present study was aimed to characterize the genetic diversity of thirty one root nodule bacterial endophytes strains from Tephrosia purpurea and Tephrosia villosa growing in Jodhpur and surrounding districts of Rajasthan (India), These two plants are widely distributed in degraded and waste land in the arid and semi arid regions of many states of India

Screening of root nodule endophytes isolated from native legumes of arid regions of India for their multiple PGP traits

Plants growing in inhospitable environment may have association with useful microbes that help them to withstand harsh conditions like poor and degraded soil, high temperature and high salinity. Isolation and screening of isolates from plants of such habitats showing plant growth promoting traits (PGP) would be useful to enrich the bank of agriculturally important microbes. In present investigation more than one hundred isolates were obtained from root nodules of ten native legumes growing in arid regions of Indian Thar desert

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Not AvailabletZnO nanoparticle induced exopolysaccharide (EPS) production from Bacillus subtilis strain JCT1 (NCBIGenBank Accession No. JN194187) is a novel approach for arid soil applications. In the series of inves-tigations, environmentally benign protocol was followed for the synthesis of ZnO nanoparticles usingextracellular enzymes obtained from Aspergillus fumigatus TFR8. Putative characterization techniqueswere employed for confirmation of size, shape, surface structure, crystalline nature and elemental pro-portion of ZnO nanoparticles. Results established an average size of ZnO nanoparticles to be 2.9 nm atleast at one dimension and oblate spherical in structure. The qualitative composition of the nanoparticlesexhibited 97.5% Zn element atom percentage. Biosynthesized ZnO nanoparticles enhanced exopolysac-charide production by 596.1% as compared to control and further EPS amelioration led to enhancedsoil aggregation (up to 82%), moisture retention (10.7–14.2%) and soil organic carbon. Soil aggre-gation stability was further confirmed by Fourier transform infra-red spectroscopy. A possible ZnOnanoparticle mediated biological mechanism for enhancing exopolysaccharide production has beendiscussed.Not Availabl

High-quality permanent draft genome sequence of Ensifer sp. PC2, isolated from a nitrogen-fixing root nodule of the legume tree (Khejri) native to the Thar Desert of India

Ensifer sp. PC2 is an aerobic, motile, Gram-negative, non-spore-forming rod that was isolated from a nitrogen-fixing nodule of the tree legume P. cineraria (L.) Druce (Khejri), which is a keystone species that grows in arid and semi-arid regions of the Indian Thar desert. Strain PC2 exists as a dominant saprophyte in alkaline soils of Western Rajasthan. It is fast growing, well-adapted to arid conditions and is able to form an effective symbiosis with several annual crop legumes as well as species of mimosoid trees and shrubs. Here we describe the features of Ensifer sp. PC2, together with genome sequence information and its annotation. The 8,458,965 bp high-quality permanent draft genome is arranged into 171 scaffolds of 171 contigs containing 8,344 protein-coding genes and 139 RNA-only encoding genes, and is one of the rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project proposal