Tobacco plants expressing the maize nitrate transporter ZmNrt2.1 exhibit altered responses of growth and gene expression to nitrate and calcium

Abstract

BackgroundNitrate uptake is a highly regulated process. Understanding the intricate interactions between nitrate availability and genetically-controlled nitrate acquisition and metabolism is essential for improving nitrogen use efficiency and increasing nitrate uptake capacity for plants grown in both nitrate-poor and nitrate-enriched environments. In this report, we introduced into tobacco (Nicotiana tabacum) the constitutively expressed maize high-affinity transporter ZmNrt2.1 gene that would bypass the tight control for the endogenous nitrate-responsive genes. By using calcium inhibitors and varying levels of NO3 −, Ca2+ and K+, we probed how the host plants were affected in their nitrate response.ResultsWe found that the ZmNrt2.1-expressing plants had better root growth than the wild type plants when Ca2+ was deficient regardless of the nitrate levels. The growth restriction associated with Ca2+-deficiency can be alleviated with a high level of K+. Furthermore, the transgenic plants exhibited altered expression patterns of several endogenous, nitrate-responsive genes, including the high- and low-affinity nitrate transporters, the Bric-a-Brac/Tramtrack/Broad protein BT2 and the transcription factor TGA-binding protein TGA1, in responding to treatments of NO3 −, K+ or inhibitors for the calcium channel and the cytosolic Ca2+-regulating phospholipase C, as compared to the wild type plants under the same treatments. Their expression was not only responsive to nitrate, but also affected by Ca2+. There were also different patterns of gene expression between roots and shoots.ConclusionOur results demonstrate the ectopic effect of the maize nitrate transporter on the host plant’s overall gene expression of nitrate sensing system, and further highlight the involvement of calcium in nitrate sensing in tobacco plants.Electronic supplementary materialThe online version of this article (10.1186/s40529-017-0203-9) contains supplementary material, which is available to authorized users.

The functional characterization of LjNRT2.4 indicates a novel, positive role of nitrate for an efficient nodule N2‐fixation activity

“…The nitrate transport capacity has been reported for the whole family of A. thaliana and O. sativa NRT2 proteins (Wei et al ., 2018; Wang et al ., 2018), as well as for the characterized NRT2 members of Brassica napus, Lycopersicon esculentum, Chrysanthemum morifolium, Cucumis sativa, Cassava and Brachypodium distachyon (Leblanc et al ., 2013; Fu et al ., 2015; Gu et al ., 2016; Li et al ., 2018; Wang et al ., 2019; L. Zou et al ., 2019). Furthermore, specific links between altered NRT2 gene expression obtained in mutant or overexpressing genetic backgrounds and nitrate‐related plant phenotypes havebeen reported in many plants, including Triticum aestivum and Zea mays (Fu et al ., 2015; He et al ., 2015; Taulemesse et al ., 2015; Gu et al ., 2016; Ibrahim et al ., 2017; Wei et al ., 2018; Li et al ., 2018; Wang et al ., 2018; Naz et al ., 2019; L. Zou et al ., 2019; Luo et al ., 2020). The reduced NO production and content detected in the Ljnrt2.4 nodules are consistent with a deficient support of the nitrate substrate (Fig.…”

Cloning and expression study of a high-affinity nitrate transporter gene from Zea mays L

“… 16 ZmNRT2.1 exhibit altered responses of growth and gene expression to nitrate and calcium. 17 An oligomer composed by two ZmNRT2.1 and two ZmNRT3.1A might be involved in the NO 3 − uptake in maize roots upon induction. 18 In addition, transcriptional studies of maize treated with saline-alkali treatment revealed that NRT2.1 was significantly up-regulated.…”