Soil alkalization is a major environmental threat that affects plant distribution and yield in northeastern China. Puccinellia tenuiflora is an alkali-tolerant grass species that is used for salt-alkali grassland restoration. However, little is known about the molecular mechanisms by which arbuscular mycorrhizal fungi (AMF) enhance P. tenuiflora responses to alkali stress. Here, metabolite profiling in P. tenuiflora seedlings with or without arbuscular mycorrhizal fungi (AMF) under alkali stress was conducted using liquid chromatography combined with time-of-flight mass spectrometry (LC/TOF-MS). The results showed that AMF colonization increased seedling biomass under alkali stress. In addition, principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) demonstrated that non-AM and AM seedlings showed different responses under alkali stress. A heat map analysis showed that the levels of 88 metabolites were significantly changed in non-AM seedlings, but those of only 31 metabolites were significantly changed in AM seedlings. Moreover, the levels of a total of 62 metabolites were significantly changed in P. tenuiflora seedlings after AMF inoculation. The results suggested that AMF inoculation significantly increased amino acid, organic acid, flavonoid and sterol contents to improve osmotic adjustment and maintain cell membrane stability under alkali stress. P. tenuiflora seedlings after AMF inoculation produced more plant hormones (salicylic acid and abscisic acid) than the non-AM seedlings, probably to enhance the antioxidant system and facilitate ion balance under stress conditions. In conclusion, these findings provide new insights into the metabolic mechanisms of P. tenuiflora seedlings with arbuscular mycorrhizal fungi under alkali conditions and clarify the role of AM in the molecular regulation of this species under alkali stress.
Our study is the first to demonstrate that PSK1 , a SKP1 -like gene homologue, is involved in salinity tolerance. Our functional characterization of PSK1 provides new insights into tree peony development. A homologous gene of S-phase kinase-associated protein1 (SKP1) was cloned from tree peony (Paeonia suffruticosa) and denoted as PSK1. The 462-bp open reading frame of PSK1 was predicted to encode a protein comprising 153 amino acids, with a molecular mass of 17 kDa. The full-length gene was 1,634 bp long and included a large 904-bp intron. PSK1 transcription was detected in all tissues, with the highest level observed in sepals, followed by leaves. Under salinity stress, overexpression of PSK1 in Arabidopsis resulted in increased germination percentages, cotyledon greening, and fresh weights relative to wild-type plants. Furthermore, transgenic Arabidopsis lines containing 35S::PSK1 displayed increased expression of genes that would be essential for reproduction and growth under salinity stress: ASK1, LEAFY, FT, and CO involved in flower development and flowering time as well as P5CS, RAB18, DREB, and SOD1-3 contributing to salinity tolerance. Our functional characterization of PSK1 adds to global knowledge of the multiple functions of previously explored SKP1-like genes in plants and sheds light on the molecular mechanism underlying its role in salinity tolerance. Our findings also provide information on the function and molecular mechanism of PSK1 in tree peony flower development, thereby revealing a theoretical basis for regulation of flowering and conferral of salinity tolerance in tree peony.
Alkali soil is a major abiotic constraint that limits plant distribution and yield in the northeast of China. Puccinellia tenuiflora is considered the most promising grass species for salt‐alkali grassland restoration. However, there is little information on the molecular mechanisms underlying how arbuscular mycorrhizal fungi (AMF) enhances P. tenuiflora stress responses in alkali‐degraded soil. In this study, AMF colonization, growth, photosynthetic pigments, and inorganic ion contents were measured. Isobaric tags for relative and absolute quantification‐based quantitative proteomic technology were employed to identify the differentially abundant proteins in P. tenuiflora seedlings with or without AMF under alkalinity stress. The results showed that AMF colonization increased seedling biomass, photosynthetic pigment contents, and K+/Na+ ratio under alkalinity stress. Moreover, a total of 598 proteins were significantly differentially regulated in P. tenuiflora seedlings after AMF inoculation under alkalinity stress compared with under alkalinity stress alone. The results showed that AMF inoculation significantly improved protein synthesis, reactive oxygen species scavenging, and nitrogen metabolism to promote the biosynthesis of osmotic substances in response to alkalinity stress. In addition, P. tenuiflora seedlings produced more energy to compensate for the energy loss caused by alkalinity stress after AMF inoculation. In conclusion, these findings provide new insights into the physiological mechanisms of the response to alkali‐degraded soil in P. tenuiflora seedlings with AMF and also clarify the role of AMF in the molecular regulation network of P. tenuiflora under alkalinity stress.
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