Cold Acclimation in Brachypodium Is Accompanied by Changes in Above-Ground Bacterial and Fungal Communities

Shifts in microbiota undoubtedly support host plants faced with abiotic stress, including low temperatures. Cold-resistant perennials prepare for freeze stress during a period of cold acclimation that can be mimicked by transfer from growing conditions to a reduced photoperiod and a temperature of 4 °C for 2–6 days. After cold acclimation, the model cereal, Brachypodium distachyon, was characterized using metagenomics supplemented with amplicon sequencing (16S ribosomal RNA gene fragments and an internal transcribed spacer region). The bacterial and fungal rhizosphere remained largely unchanged from that of non-acclimated plants. However, leaf samples representing bacterial and fungal communities of the endo- and phyllospheres significantly changed. For example, a plant-beneficial bacterium, Streptomyces sp. M2, increased more than 200-fold in relative abundance in cold-acclimated leaves, and this increase correlated with a striking decrease in the abundance of Pseudomonas syringae (from 8% to zero). This change is of consequence to the host, since P. syringae is a ubiquitous ice-nucleating phytopathogen responsible for devastating frost events in crops. We posit that a responsive above-ground bacterial and fungal community interacts with Brachypodium’s low temperature and anti-pathogen signalling networks to help ensure survival in subsequent freeze events, underscoring the importance of inter-kingdom partnerships in the response to cold stress.

Physiological effects of different stubble height and freeze-thaw stress on Secale cereale L. seedlings

Background As a biennial plant, Secale cereale L is usually harvested in the autumn in the northern part of China where the temperature difference between day and night is of great disparity Through the pot experiment, the seedlings were cut to 2, 6 and 10 cm stubble height, and the simulated freeze-thaw (FT) stress (10/− 5 °C) was carried out after 6 days regrowth. The physiological effects of FT with different stubble height were revealed by analyzing the relative water content (RWC), osmotic adjustment substance concentration (soluble sugar and protein), membrane peroxidation (MDA) and catalase (CAT) activity. Results The results demonstrated that under freeze stress (− 5 °C), the content of soluble protein and MDA decreased and the seedlings of 2 cm treatment kept higher level of soluble protein and MDA, while the seedlings of 6 and 10 cm treatments kept higher level of the RWC, soluble sugar content, and CAT activity. After FT stress, the content of soluble sugar and protein, RWC in the 6 cm treatment were higher than those in 2 cm and 10 cm treatments, and the CAT activity in 10 cm treatment was the highest while the MDA content is lower. Conclusion These data suggest that keeping high stubble height is more adaptive for short-term FT stress.

Physiological Effects of Different Stubble Height and Freeze-Thaw Stress on Secale cereale L. Seedlings

Background: As a biennial plant, Secale cereale L is usually harvested in the autumn in the northern part of China where the temperature difference between day and night is of great disparity Through the pot experiment, the seedlings were cut to 2, 6 and 10 cm stubble height, and the simulated freeze-thaw (FT) stress (10/-5℃) was carried out after 6 days regrowth. The physiological effects of FT with different stubble height were revealed by analyzing the relative water content (RWC), osmotic adjustment substance concentration (soluble sugar and protein), membrane peroxidation (MDA) and catalase (CAT) activity. Results: The results demonstrated that under freeze stress (-5℃), the content of soluble protein and MDA decreased and the seedlings of 2 cm treatment kept higher level of soluble protein and MDA, while the seedlings of 6 and 10 cm treatments kept higher level of the RWC, soluble sugar content, and CAT activity. After FT stress, the content of soluble sugar and protein, RWC in the 6 cm treatment were higher than those in 2 cm and 10 cm treatments, and the CAT activity in 10 cm treatment was the highest while the MDA content is lower.Conclusion: These data suggest that keeping high stubble height is more adaptive for short-term FT stress.

Comparative transcriptome analysis of two different genotypes of wheat (Triticum aestivum L.) in response to spring freeze-stress

Frequent cold spells in spring can lead to significant yield loss in wheat, which seriously affects the spike differentiation and formation. Aikang58 (AK58) and Zhengmai366 (ZM366) are two important wheat cultivars in China, especially in the main wheat-producing areas of the Yellow River and the Huaihe River. This study investigated the response of AK58 and ZM366 to spring-freeze stress using comparative transcriptome analysis. The yield per plant decreased by 12% (AK58) and 89% (ZM366) after three days of low-temperature treatment during the differentiation of pistil and stamen primordia. Low-temperature treatment had a greater effect on the seed-setting rate of ZM366 than of AK58. RNA-seq analysis of AK58 and ZM366 treated at low temperature found 5835 and 8413 differentially expressed genes (DEGs), respectively, of which 3434 genes were common to both varieties. Further analysis of the higher cold resistance in spring of AK58 compared to ZM366 found: a) In response to low-temperature stress, the expression of gene encoding of antioxidant enzymes in AK58 were much higher than that in ZM366; b) The DEGs expression in the hormone signal transduction pathway under low temperature conditions found that AK58 activated abscisic acid and jasmonic acid signal transduction pathway more effectively; c) Under low-temperature conditions, the metabolic pathway for selenium compounds in AK58 was inhibited; d) Low-temperature stress caused abnormal expression of flowering genes in ZM366, resulting in the final seed setting rate of ZM366 being far lower than AK58. These results provide a sound basis for further screening of genes that may improve the cold resistance of wheat in spring.

Ice-recrystallization inhibiting polymers protect proteins against freeze-stress and enable glycerol-free cryostorage

Antifreeze-protein mimic polymers are shown to enable solvent-free storage of important proteins for therapy and biotechnology by modulating ice growth.