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Comparative Transcriptomics and Proteomics Analyses of Leaves Reveals a Freezing Stress-Responsive Molecular Network in Winter Rapeseed (Brassica rapa L.).

ABSTRACT: Winter rapeseed is susceptible to low temperature during winter in Northwest China, which could lead to a severe reduction of crop production. The freezing temperature could stress the whole plant, especially the leaf, and ultimately harm the survival rate of winter rapeseed. However, the molecular mechanism underlying freezing tolerance is still unclear in winter rapeseed. In this study, a comprehensive investigation of winter rapeseed freezing tolerance was conducted at the levels of transcript, protein, and physiology and biochemistry, using a pair of freezing-sensitive and freezing-resistant cultivars NQF24 and 17NTS57. There were 4,319 unique differentially expressed genes (DEGs) and 137 unique differentially abundant proteins (DAPs) between two cultivars identified in leaf under freezing stress. Function enrichment analysis showed that most of the enriched DEGs and DAPs were involved in plant hormone signal transduction, alpha-linolenic/linoleic acid metabolism, peroxisome, glutathione metabolism, fatty acid degradation, and secondary metabolite biosynthesis pathways. Based on our findings, it was speculated that freezing tolerance formation is caused by increased signal transduction, enhanced biosynthesis of protein, secondary metabolites, and plant hormones, elevated energy supply, greater reactive oxygen species scavenging, and lower lipid peroxidation as well as stronger cell stability in leaf under freezing stress. These results provide a comprehensive profile of leaf response under freezing stress, which have potential to be used as selection indicators of breeding programs to improve freezing tolerance in rapeseed.

SUBMITTER: Wei J

PROVIDER: S-EPMC8113625 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Two Chinese cabbage (Brassica rapa ssp. pekinensis) inbred lines, Chiifu (smaple A) and Kenshin (Smaple B), were grown for approximately 4 weeks in a growth chamber at 22degreesC under a 16 h light/8 h dark photoperiod with a photon flux density of 140 umol m-2 s-1. For microarray analysis, plants were exposed to a temperature of -4degreesC for 4 h, and shoots were sampled. Total RNA was isolated from the samples using an Easy-BLUETM Total RNA Extraction Kit (Invitrogen, NY, U.S.A.) and was then purified using an RNeasy MinEluteTM Cleanup Kit (Qiagen, Germany). Mircroarray experiments were carried out using Brassica 24K Oligo Microarray. RNA were prepared from each plant sample and 10 ug of total RNA were used for cDNA synthesis by using Superscript Double-Stranded cDNA Synthesis Kit (Invitrogen, NY, U.S.A.). Following cDNA synthesis, remaining RNA was removed by the addition of RNaseA and the cDNA was precipitated following phenol/chloroform extraction. The cDNA pellet was rehydrated and used for Cy3-labelling. For the synthesis of Cy3-labeled target DNA fragments, 1 ug of double strand cDNA was mixed with 40 ul (1 OD) of Cy3-9 mer primers (Sigma-Aldrich) and the total volume was adjusted to 80 ul with deionized water. After heating at 98degreesC for 10 min, 10 uL of dNTP mix (10 mM each) and 2 ul of Klenow fragment (NEB; 50 units/ul) were added and the reaction was incubated at 37degreesC for 2 h. Finally, the reaction was stopped by the addition of 10 ul of 0.5 M EDTA. Labeled DNA fragments were precipitated with isopropanol and rehydrated with water. The concentration of each sample was determined using spectrophotometer. For hybridization, 13 ug of the labeled DNA fragment was mixed with hybridization buffer (NimbleGen) and then hybridized with the microarray using a MAUI hybridization chamber (Biomicro) at 42degreesC for 16 h. Following hybridization, the microarray was washed with wash solution I, II, and III (NimbleGen), and then dried in a dark desiccator. The microarray slide was scanned using GenePix scanner 4000B (Axon) and the spot intensities were analyzed using a NimbleScan (NimbleGen). The normal distribution of Cy3 intensities was tested by qqline. The data was normalized and processed with cubic spline normalization using quantiles to adjust signal variations between chips and with Rubust Multi-Chip Analysis (RMA) using a median polish algorithm implemented in NimbleScan software (NimbleGen). Two biological replicates were carried out.

Project description:Winter rapeseed is not only an important oilseed crop, but also a winter cover crop in Northern China, where its production was severely limited by freezing stress. As an overwinter crop, the production is severely limited by freezing stress. Therefore, understanding the physiological and molecular mechanism of winter rapeseed (Brassica napus L.) in freezing stress responses becomes essential for the improvement and development of freezing-tolerant varieties of Brassica napus. In this study, morphological, physiological, ultrastructure and transcriptome changes in the Brassica napus line "2016TS(G)10" (freezing-tolerance line) that was exposed to -2 °C for 0 h, 1 h, 3 h and 24 h were characterized. The results showed that freezing stress caused seedling dehydration, and chloroplast dilation and degradation. The content of malondialdehyde (MDA), proline, soluble protein and soluble sugars were increased, as well as the relative electrolyte leakage (REL) which was significantly increased at frozen 24 h. Subsequently, RNA-seq analysis revealed a total of 98,672 UniGenes that were annotated in Brassica napus and 3905 UniGenes were identified as differentially expressed genes after being exposed to freezing stress. Among these genes, 2312 (59.21%) were up-regulated and 1593 (40.79%) were down-regulated. Most of these DEGs were significantly annotated in the carbohydrates and energy metabolism, signal transduction, amino acid metabolism and translation. Most of the up-regulated DEGs were especially enriched in plant hormone signal transduction, starch and sucrose metabolism pathways. Transcription factor enrichment analysis showed that the AP2/ERF, WRKY and MYB families were also significantly changed. Furthermore, 20 DEGs were selected to validate the transcriptome profiles via quantitative real-time PCR (qRT-PCR). In conclusion, the results provide an overall view of the dynamic changes in physiology and insights into the molecular regulation mechanisms of winter Brassica napus in response to freezing treatment, expanding our understanding on the complex molecular mechanism in plant response to freezing stress.

Project description:Winter rapeseed (Brassica rapa L.) is a major oilseed crop in Northern China, where its production was severely affected by chilling and freezing stress. However, not much is known about the role of differentially accumulated proteins (DAPs) during the chilling and freezing stress. In this study, isobaric tag for relative and absolute quantification (iTRAQ) technology was performed to identify DAPs under freezing stress. To explore the molecular mechanisms of cold stress tolerance at the cellular and protein levels, the morphological and physiological differences in the shoot apical meristem (SAM) of two winter rapeseed varieties, Longyou 7 (cold-tolerant) and Lenox (cold-sensitive), were explored in field-grown plants. Compared to Lenox, Longyou 7 had a lower SAM height and higher collar diameter. The level of malondialdehyde (MDA) and indole-3-acetic acid (IAA) content was also decreased. Simultaneously, the soluble sugars (SS) content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, soluble protein (SP) content, and collar diameter were increased in Longyou 7 as compared to Lenox. A total of 6330 proteins were identified. Among this, 98, 107, 183 and 111 DAPs were expressed in L7 CK/Le CK, L7 d/Le d, Le d/Le CK and L7 d/L7 CK, respectively. Quantitative real-time PCR (RT-qPCR) analysis of the coding genes for seventeen randomly selected DAPs was performed for validation. These DAPs were identified based on gene ontology enrichment analysis, which revealed that glutathione transferase activity, carbohydrate-binding, glutathione binding, metabolic process, and IAA response were closely associated with the cold stress response. In addition, some cold-induced proteins, such as glutathione S-transferase phi 2(GSTF2), might play an essential role during cold acclimation in the SAM of Brassica rapa. The present study provides valuable information on the involvement of DAPs during cold stress responses in Brassica rapa L, and hence could be used for breeding experiments.

Project description:BACKGROUND:Low temperature is a major abiotic stress affecting the production of rapeseed in China by impeding plant growth and development. A comprehensive knowledge of small-RNA expression pattern in Brassica rapa under cold stress could improve our knowledge of microRNA-mediated stress responses. RESULTS:A total of 353 cold-responsive miRNAs, 84 putative novel and 269 conserved miRNAs, were identified from the leaves and roots of two winter turnip rape varieties 'Longyou 7' (cold-tolerant) and 'Tianyou 4' (cold-sensitive), which were stressed under -?4 °C for 8 h. Eight conserved (miR166h-3p-1, miR398b-3p, miR398b-3p-1, miR408d, miR156a-5p, miR396h, miR845a-1, miR166u) and two novel miRNAs (Bra-novel-miR3153-5p and Bra-novel-miR3172-5p) were differentially expressed in leaves of 'Longyou 7' under cold stress. Bra-novel-miR3936-5p was up-regulated in roots of 'Longyou 7' under cold stress. Four and five conserved miRNAs were differentially expressed in leaves and roots of 'Tianyou 4' after cold stress. Besides, we found two conserved miRNAs (miR319e and miR166m-2) were down-regulated in non-stressed roots of 'Longyou 7' compared with 'Tianyou 4'. After cold stress, we found two and eight miRNAs were differentially expressed in leaves and roots of 'Longyou 7' compared with 'Tianyou 4'. The differentially expressed miRNAs between two cultivars under cold stress include novel miRNAs and the members of the miR166 and miR319 families. A total of 211 target genes for 15 known miRNAs and two novel miRNAs were predicted by bioinformatic analysis, mainly involved in metabolic processes and stress responses. Five differentially expressed miRNAs and predicted target genes were confirmed by quantitative reverse transcription PCR, and the expressional changes of target genes were negatively correlated to differentially expressed miRNAs. Our data indicated that some candidate miRNAs (e.g., miR166e, miR319, and Bra-novel-miR3936-5p) may play important roles in plant response to cold stress. CONCLUSIONS:Our work indicates that miRNA and putative target genes mediated metabolic processes and stress responses are significant to cold tolerance in B. rapa.

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Comparative Transcriptomics and Proteomics Analyses of Leaves Reveals a Freezing Stress-Responsive Molecular Network in Winter Rapeseed (Brassica rapa L.).

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