Abstract
Understanding the molecular mechanisms in wheat response to nitrogen (N) fertilizer will help us to breed wheat varieties with improved yield and N use efficiency. Here, we cloned TaLAMP1-3A, -3B, and -3D, which were upregulated in roots and shoots of wheat by low N availability. In a hydroponic culture, lateral root length and N uptake were decreased in both overexpression and knockdown of TaLAMP1 at the seedling stage. In the field experiment with normal N supply, the grain yield of overexpression of TaLAMP1-3B is significantly reduced (14.5%), and the knockdown of TaLAMP1 was significantly reduced (15.5%). The grain number per spike of overexpression of TaLAMP1-3B was significantly increased (7.2%), but the spike number was significantly reduced (19.2%) compared with wild type (WT), although the grain number per spike of knockdown of TaLAMP1 was significantly decreased (15.3%), with no difference in the spike number compared with WT. Combined with the agronomic data from the field experiment of normal N and low N, both overexpression and knockdown of TaLAMP1 inhibited yield response to N fertilizer. Overexpressing TaLAMP1-3B greatly increased grain N concentration with no significant detrimental effect on grain yield under low N conditions; TaLAMP1-3 B is therefore valuable in engineering wheat for low input agriculture. These results suggested that TaLAMP1 is critical for wheat adaptation to N availability and in shaping plant architecture by regulating spike number per plant and grain number per spike. Optimizing TaLAMP1 expression may facilitate wheat breeding with improved yield, grain N concentration, and yield responses to N fertilizer.
Highlights
Nitrogen (N) is the most important macronutrient required for crop growth and development
Phylogenetic assays showed that TaLAMP1-3A, 3B, and 3D clustered in the same clade with AtLAMP1 (Figure 2)
At least two of the knockdown lines had higher plant height (Figure 6A) but lower grain yield (Figure 6C), grain number per spike (Figure 6F), and grain weight per spike (Figure 6G) than wild type (WT). These results indicated that altering TaLAMP1 expression changed plant architecture reflecting by plant height, spike number per plant, and grain number per spike, and the phenotypes of the agronomic traits in the transgenic lines depended on N supply levels
Summary
Nitrogen (N) is the most important macronutrient required for crop growth and development. Crops with a higher N use efficiency (NUE) is essential for the sustainability of agriculture, which could minimize the loss of N and reduce environmental pollution. NUE is defined as the grain yield produced per unit of N available in the soils and can be divided into two plant physiological components: N uptake efficiency and N. During biomass formation, there is the amount of N uptake, storage, and assimilation into amino acids and other important nitrogenous compounds. A variety of nitrate and ammonium transporters function in N absorption by roots (Crawford and Glass, 1998; Forde, 2000; Howitt and Udvardi, 2000; O’Brien et al, 2016) and a number of enzymes for assimilation and transfer of the absorbed N into amino acids and other compounds, such as nitrate reductase, glutamine synthetase, and glutamate synthase (Campbell, 1988; Lam et al, 1996; Näsholm et al, 2009)
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