Comparison of transcriptome and metabolome analysis revealed differences in cold resistant metabolic pathways in different apple cultivars under low temperature stress

Freezing injury in winter is an important abiotic stress that seriously affects plant growth and development.Deciduous fruit trees resist freezing injury by inducing dormancy.However,different cultivars of the same species have different cold resistance strategies.Little is known about the molecular mechanism of apple trees in response to freezing injury during winter dormancy.Therefore,in this study,1-year-old branches of the cold-resistant cultivar‘Hanfu’(HF)and the cold-sensitive cultivar‘Changfuji No.2’(CF)were used to explore their cold resistance through physiological,biochemical,transcriptomics,and metabolomics analyses.Combining physiological and biochemical data,we found that HF had a stronger osmotic regulation ability and antioxidant enzyme activity than CF,as well as stronger cold resistance.The functional enrichment analysis showed that both cultivars were significantly enriched in pathways related to signal transduction,hormone regulation,and sugar metabolism under freezing stress.In addition,the differentially expressed genes(DEGs)encoding galactinol synthase,raffinose synthase,and stachyose synthetase in raffinose family oligosaccharides(RFOs)metabolic pathways were upregulated in HF,and raffinose and stachyose were accumulated,while their contents in CF were lower.HF accumulated 4-aminobutyric acid,spermidine,and ascorbic acid to scavenge reactive oxygen species(ROS).While the contents of oxidized glutathione,vitamin C,glutathione,and spermidine in CF decreased under freezing stress,consequently,the ability to scavenge ROS was low.Furthermore,the transcription factors apetala 2/ethylene responsive factor(AP2/ERF)and WRKY were strongly induced under freezing stress.In summary,the difference in key metabolic components of HF and CF under freezing stress is the major factor affecting their difference in cold resistance.The obtained results deepen our understanding of the cold resistance mechanism in apple trees in response to freezing injury during dormancy.

Effect of glucose on the soil bacterial diversity and function in the rhizosphere of Cerasus sachalinensis

Most cherry orchards in China have low organic carbon content,though carbon is very important for plant growth.The changes in soil carbon and bacterial diversity were determined after different amounts of 12C-glucose were added to the rhizosphere of Cerasus sachalinensis.Soil bacteria diversity was measured using high throughput sequencing,and bacteria containing 13C-glucose were identified using DNA-SIP methods.The results demonstrated that soil microbial biomass carbon(MBC)content and the soil respiratory rate were increased at 3 and 7 days after adding glucose.The soil organic carbon(SOC)content was decreased on the 7th day in the treatment where the added glucose-C was equivalent to the MBC content.SOC content was decreased on the 15th day after adding glucose-C equivalent to five times that of the soil MBC.Compared to the controls,the relative abundance of taxa at the phylum level displayed no significant change in the treatments with glucose-C added as 10%and equal amount of soil MBC 3–30 days after treatment.However,the relative abundance of Proteobacteria increased significantly in the treatment with the addition of glucose-C equivalent to five times of soil MBC.The main changes were observed in the bacteria in several genera including A4,Flavisolibacter,Aquicella,and Candidatus Solibacter.DNA-SIP results indicated that the relative abundance of the Proteobacteria and Pseudomonas was the highest;these were the primary bacteria phylum and genus,respectively,from day 3 to day 15.In conclusion,the changing pattern demonstrated that with the addition of more glucose,the range of the bacterial communities changed more.Proteobacteria and Pseudomonas may be the bacteria promoting priming effect.

Production of reactive oxygen species by PuRBOHF is critical for stone cell development in pear fruit

The production of reactive oxygen species(ROS)by NADPH oxidase,which is also referred to as respiratory burst oxidase homolog(RBOH),affects several processes in plants.However,the role of RBOHs in cell wall lignification is not well understood.In this study,we show that PuRBOHF,an RBOH isoform,plays an important role in secondary wall formation in pear stone cells.ROS were closely associated with lignin deposition and stone cell formation according to microscopy data.In addition,according to the results of an in situ hybridization analysis,the stage-specific expression of PuRBOHF was higher in stone cells than in cells of other flesh tissues.Inhibitors of RBOH activity suppressed ROS accumulation and stone cell lignification in pear fruit.Moreover,transient overexpression of PuRBOHF caused significant changes in the amount of ROS and lignin that accumulated in pear fruit and flesh calli.We further showed that PuMYB169 regulates PuRBOHF expression,while PuRBOHF-derived ROS induces the transcription of PuPOD2 and PuLAC2.The findings of this study indicate that PuRBOHF-mediated ROS production,which is regulated by a lignin-related transcriptional network,is essential for monolignol polymerization and stone cell formation in pear fruit.