Abstract
In the long-term evolutionary process, Achnatherum inebrians and seed-borne endophytic fungi, Epichloë gansuensis, formed a mutually beneficial symbiosis relationship, and Epichloë gansuensis has an important biological role in improving the tolerance of host grasses to abiotic stress. In this work, we first assessed the effects of Epichloë gansuensis on dry weight, the content of C, N, P and metal ions, and metabolic pathway of amino acids, and phosphorus utilization efficiency (PUE) of Achnatherum inebrians at low P stress. Our results showed that the dry weights, the content of alanine, arginine, aspartic acid, glycine, glutamine, glutamic acid, L-asparagine, lysine, phenylalanine, proline, serine, threonine, and tryptophan were higher in leaves of Epichloë gansuensis-infected (E+) Achnatherum inebrians than Epichloë gansuensis-uninfected (E−) Achnatherum inebrians at low P stress. Further, Epichloë gansuensis increased C content of roots compared to the root of E− plant at 0.01 mM P and 0.5 mM P; Epichloë gansuensis increased K content of leaves compared to the leaf of E− plant at 0.01 mM P and 0.5 mM P. Epichloë gansuensis reduced Ca content of roots compared to the root of E− plant at 0.01 mM P and 0.5 mM P; Epichloë gansuensis reduced the content of Mg and Fe in leaves compared to the leaf of E− plant at 0.01 mM P and 0.5 mM P. In addition, at low P stress, Epichloë gansuensis most probably influenced aspartate and glutamate metabolism; valine, leucine, and isoleucine biosynthesis in leaves; and arginine and proline metabolism; alanine, aspartate, and glutamate metabolism in roots. Epichloë gansuensis also affected the content of organic acid and stress-related metabolites at low P stress. In conclusion, Epichloë gansuensis improves Achnatherum inebrians growth at low P stress by regulating the metabolic pathway of amino acids, amino acids content, organic acid content, and increasing PUE.
Highlights
We found that Epichloë gansuensis significantly increases the dry weight of leaves compared with the E− leaves at 0.01 mM P, and the leaves dry weight of E+ seedling was increased by 30.5% than that of E− seedling at the low P stress
We found that low P stress significantly increased the leaves C content of E+ Achnatherum inebrians compared with 0.5 mM P, and the C content of E+ leaves at 0.01 mM P was
We found that phenylalanine metabolism, isoquinoline alkaloid biosynthesis, cyanoamino acid metabolism, alanine, aspartate, and glutamate metabolism in LE+ may be the most correlative pathways regulated by low P stress (Figure 8b)
Summary
Phosphorus (P) is an important macronutrient for plant life cycle, including growth and development, which is involved in a variety of physiology processes. It is significant for the synthesis of some important compounds and regulation of metabolic pathways, such as membrane lipids, nucleic acids, ATP, and phosphorylation intermediates [1]. People apply a lot of phosphate fertilizer to enhance the content of soil phosphorus and crop yield [3]. In order to maintain the sustainable development of agriculture and food security under the global climate change and improve the phosphorus absorption and utilization efficiency of plant, breeding grasses with high P efficiency is an efficient strategy to deal with low P availability of soil
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