AUTHOR=Kong Lingan , Zhang Yunxiu , Du Wanying , Xia Haiyong , Fan Shoujin , Zhang Bin 

TITLE=Signaling Responses to N Starvation: Focusing on Wheat and Filling the Putative Gaps With Findings Obtained in Other Plants. A Review

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.656696

DOI=10.3389/fpls.2021.656696

ISSN=1664-462X

ABSTRACT=Wheat is one of most important food crops worldwide. In the past decades, increasing fertilizers, especially nitrogen (N), has been used to maximize wheat productivity. However, a large proportion of the N is not used by plants, being lost into the environments and causing serious environmental pollution. Therefore, to achieve a low N optimum via efficient physiological and biochemical processes in wheat grown in low-N conditions is pivotal important for agricultural sustainability. Despite N stress-related research on wheat captures an exciting field, how this plant adapts and responds to N starvation is far from being understood. This review summarizes the current knowledge on the signaling mechanisms in wheat plants responding to N starvation. Further, we conceivably fill the putative gaps with knowledge from other plants, mainly including Arabidopsis, maize and rice. The development of optimized root system architecture (RSA), improved N acquisition and assimilation as well as fine-tuned autophagy is as strategies to respond to N starvation. As secondary messengers and signal molecules, calcium, nitric oxide, reactive oxygen species and phytohormones play essential roles in sensing environmental N starvation and tranducing this signal into an adjustment of N transporters and phenotypic adaptation. The multifaceted functions of miRNAs, transcript factors and protein reversible phosphorylation in regulating the expression of their target genes (proteins) for low-N tolerance are also summarized. We tried to construct regulatory networks in RSA modification, N uptake, transport, assimilation and remobilization using these modules.