Genome-wide identification and analysis of high-affinity nitrate transporter 2 (NRT2) family genes in rapeseed (Brassica napus L.) and their responses to various stresses

Abstract

Background High-affinity nitrate transporter 2 (NRT2) genes have been implicated in nitrate absorption and remobilization under nitrogen (N) starvation stress in many plant species, yet little is known about this gene family respond to various stresses often occurs in the production of rapeseed (Brassica napus L.). Results This report details identification of 17 NRT2 gene family members in rapeseed, as well as, assessment of their expression profiles using RNA-seq analysis and qRT-PCR assays. In this study, all BnNRT2.1 members, BnNRT2.2a and BnNRT2.4a were specifically expressed in root tissues, while BnNRT2.7a and BnNRT2.7b were mainly expressed in aerial parts, including as the predominantly expressed NRT2 genes detected in seeds. This pattern of shoot NRT expression, along with homology to an Arabidopsis NRT expressed in seeds, strongly suggests that both BnNRT2.7 genes play roles in seed nitrate accumulation. Another rapeseed NRT, BnNRT2.5 s, exhibited intermediate expression, with transcripts detected in both shoot and root tissues. Functionality of BnNRT2s genes was further outlined by testing for adaptive responses in expression to exposure to a series of environmental stresses, including N, phosphorus (P) or potassium (K) deficiency, waterlogging and drought. In these tests, most NRT2 gene members were up-regulated by N starvation and restricted by the other stresses tested herein. In contrast to this overall trend, transcription of BnNRT2.1a was up-regulated under waterlogging and K deficiency stress, and BnNRT2.5 s was up-regulated in roots subjected to waterlogging. Furthermore, the mRNA levels of BnNRT2.7 s were enhanced under both waterlogging stress and P or K deficiency conditions. These results suggest that these three BnNRT2 genes might participate in crosstalk among different stress response pathways. Conclusions The results presented here outline a diverse set of NRT2 genes present in the rapeseed genome that collectively carry out specific functions throughout rapeseed development, while also responding not just to N deficiency, but also to several other stresses. Targeting of individual BnNRT2 members that coordinate rapeseed nitrate uptake and transport in response to cues from multiple stress response pathways could significantly expand the genetic resources available for improving rapeseed resistance to environmental stresses.

Genome Identification and Expression Analysis of GRAS Family Related to Development, Hormone and Pathogen Stress in Brachypodium distachyon

“…The qRT-PCR reaction sample adopts 20 µl systems, of which 10 µM forward and reverse primers are 0.4 µl each, TransStart Tip Green qPCR SuperMix 10 µl, template 2 µl, 7.2 µl ddH 2 O. qRT-PCR conditions were as follows: 94 • C for 1 min, 30 cycles (94 • C for 20 s, 56 • C for 15 s, and 1 min at 72 • C), and 72 • C for 5 min. qRT-PCR was performed using the CFX 96 qPCR instrument (BioRad, California, USA) (Tong et al, 2020). The BdUBC gene was used as the internal reference.…”

K Deprivation Modulates the Primary Metabolites and Increases Putrescine Concentration in Brassica napus

“…Different studies have focused on the effect of K deficiency on specific organs or physiological parameters in rapeseed plant ( Lu et al, 2016 , 2019 ; Tong et al, 2020 ). In this study, an effort was undertaken to investigate the overall response of B. napus to the lack of K nutrition.…”

Phylogenomic and Microsynteny Analysis Provides Evidence of Genome Arrangements of High-Affinity Nitrate Transporter Gene Families of Plants

“…Among these transport systems are those with low affinity (LATS), which operate when external concentrations of NO 3 − are greater than 1 mM, and those with high affinity (HATS), which operate at micromolar concentrations of NO 3 − [ 6 ]. HATS may be key to nitrate absorption under conditions of low availability, where HATS activity may have hundreds of times more affinity for N, thereby supplanting LATS activity [ 7 , 8 ].…”

“…These proteins are identified by the presence of a characteristic domain of NAR2 proteins [ 8 , 20 , 22 ]. In addition to Arabidopsis, six NRT2 and five NRT3 have been identified in Populus trichocarpa [ 32 ], three NRT2 and one NRT3 in Ananas comosus [ 33 ], four NRT2 in Zea may [ 34 ], 17 NRT2 in Brassica napus L. [ 7 ], and 10 NRT2 and three NRT3 in Hordeum vulgare L. [ 35 ]. Functional and molecular studies of high-affinity transporters have been partially carried out in other species, such as Lotus japonicus and Medicago truncatula [ 36 ], Zostera marina [ 37 ], Triticum aestivum [ 38 ], Capsicum chinense [ 21 ], Spinacia oleracea L. [ 17 ], and Malus domestica [ 39 ], among others.…”

“…Comparative analysis coupled to microsynteny would help to understand the evolutionary trajectory of genes and ultimately of key innovations into species [ 43 , 44 , 45 , 46 , 47 ]. Synteny studies have been conducted for the analysis of nitrate transporters in a few species, comparing them in a limited way with the model species A. thaliana [ 7 , 33 ]. However, the analysis of multiple genomes would provide a more solid view of the evolutionary process [ 48 ].…”