Differential Morpho-Physiological, Ionomic, and Phytohormone Profiles, and Genome-Wide Expression Profiling Involving the Tolerance of Allohexaploid Wheat (Triticum aestivum L.) to Nitrogen Limitation

Common
wheat (Triticum aestivum L.)
is a global staple food, while nitrogen (N) limitation severely hinders
plant growth, seed yield, and grain quality of wheat. Genetic variations
in the responses to low N stresses among allohexaploid wheat (AABBDD,
2n = 6x = 42) genotypes emphasize
the complicated regulatory mechanisms underlying low N tolerance and
N use efficiency (NUE). In this study, hydroponic culture, inductively
coupled plasma mass spectrometry, noninvasive microtest, high-performance
liquid chromatography, RNA-seq, and bioinformatics were used to determine
the differential growth performance, ionome and phytohormone profiles,
and genome-wide expression profiling of wheat plants grown under high
N and low N conditions. Transcriptional profiling of NPFs, NRT2s,
CLCs, SLACs/SLAHs, AAPs, UPSs, NIAs, and GSs characterized the core
members, such as TaNPF6.3-6D, TaNRT2.3–3D, TaNIA1–6B, TaGLN1;2–4B, TaAAP14–5A/5D, and TaUPS2–5A, involved in the efficient transport and
assimilation of nitrate and organic N nutrients. The low-N-sensitivity
wheat cultivar XM26 showed obvious leaf chlorosis and accumulated
higher levels of ABA, JA, and SA than the low-N-tolerant ZM578 under
N limitation. The TaMYB59–3D-TaNPF7.3/NRT1.5–6D module-mediated shoot-to-root
translocation and leaf remobilization of nitrate was proposed as an
important pathway regulating the differential responses between ZM578
and XM26 to low N. This study provides some elite candidate genes
for the selection and breeding of wheat germplasms with low N tolerance
and high NUE.