Nystose regulates the response of rice roots to cold stress via multiple signaling pathways: A comparative proteomics analysis

Metabolic Profiling of Oryza sativa L. Triggered by Chilling Stress Using Ultraperformance Liquid Chromatography Coupled with Quadrupole/Time-of-Flight Mass Spectrometry (UPLC-QTOF-MS) with Transcriptome Analysis

Low temperature, a major abiotic stress, often causes molecular changes in crops, which leads to metabolic disturbances and probably affects crop yield. In this study, chilling stress induced distinct metabolic profiles associated with transcriptome regulation, exhibiting great metabolic differences between Qiutianxiaoting (japonica) and 93-11 (indica). In total, 41 and 58 differential metabolites were screened and identified in Qiutianxiaoting and 93-11, respectively. Five key metabolites were screened in response to chilling stress, which were involved or related to different metabolic pathways. Moreover, starch and sucrose metabolism, aminoacyl-tRNA biosynthesis, and phenylpropanoid biosynthesis were significantly enriched in Qiutianxiaoting to maintain cellular homeostasis. Aminoacyl-tRNA biosynthesis and antioxidation metabolism were significantly enriched in 93-11, but disorders of the metabolome and transcriptome occurred at recovery stage. The results could provide some useful information for in-depth understanding of cold-resistant mechanisms, as well as reference for the selection and breeding of rice varieties.

Fructan oligosaccharide priming alters apoplastic sugar dynamics and improves resistance against Botrytis cinerea in chicory

Carbohydrates such as fructans can be involved in priming or defence stimulation, and hence potentially provide new strategies for crop protection against biotic stress. Chicory (Cichorium intybus) is a model plant for fructan research and is a crop with many known health benefits. Using the chicory-Botrytis cinerea pathosystem, we tested the effectiveness of fructan-induced immunity, focussing on different plant and microbial fructans. Sugar dynamics were followed after priming and subsequent pathogen infection. Our results indicated that many higher plants might detect extracellular levan oligosaccharides (LOS) of microbial origin, while chicory also detects extracellular small inulin-type fructooligosaccharides (FOS) of endogenous origin, thus differing from the findings of previous fructan priming studies. No clear positive effects were observed for inulin or mixed-type fructans. An elicitor-specific burst of reactive oxygen species was observed for sulfated LOS, while FOS and LOS both behaved as genuine priming agents. In addition, a direct antifungal effect was observed for sulfated LOS. Intriguingly, LOS priming led to a temporary increase in apoplastic sugar concentrations, mainly glucose, which could trigger downstream responses. Total sugar and starch contents in total extracts of LOS-primed leaves were higher after leaf detachment, indicating they could maintain their metabolic activity. Our results indicate the importance of balancing intra- and extracellular sugar levels (osmotic balance) in the context of 'sweet immunity' pathways.

Comparative Proteomics Reveals the Difference in Root Cold Resistance between Vitis. riparia × V. labrusca and Cabernet Sauvignon in Response to Freezing Temperature

Grapevines, bearing fruit containing large amounts of bioactive metabolites that offer health benefits, are widely cultivated around the world. However, the cold damage incurred when grown outside in extremely low temperatures during the overwintering stage limits the expansion of production. Although the morphological, biochemical, and molecular levels in different Vitis species exposed to different temperatures have been investigated, differential expression of proteins in roots is still limited. Here, the roots of cold-resistant (Vitis. riparia × V. labrusca, T1) and cold-sensitive varieties (Cabernet Sauvignon, T3) at -4 °C, and also at -15 °C for the former (T2), were measured by iTRAQ-based proteomic analysis. Expression levels of genes encoding candidate proteins were validated by qRT-PCR, and the root activities during different treatments were determined using a triphenyl tetrazolium chloride method. The results show that the root activity of the cold-resistant variety was greater than that of the cold-sensitive variety, and it declined with the decrease in temperature. A total of 25 proteins were differentially co-expressed in T2 vs. T1 and T1 vs. T3, and these proteins were involved in stress response, bio-signaling, metabolism, energy, and translation. The relative expression levels of the 13 selected genes were consistent with their fold-change values of proteins. The signature translation patterns for the roots during spatio-temporal treatments of different varieties at different temperatures provide insight into the differential mechanisms of cold resistance of grapevine.