Mechanistic Insights Into Trehalose-Mediated Cold Stress Tolerance in Rapeseed (Brassica napus L.) Seedlings.

Cold stress (CS) severely affects several physiological, biochemical, and molecular mechanisms and limits the growth and production of rapeseed (Brassica napus L.). Trehalose (Tre) acts as a growth modulator, which is extensively used to improve the tolerance to multiple plant stresses. Further, Tre also serves as an external force in inducing plant signaling molecules, regulating the expression of stress-responsive genes, and enhancing the CS tolerance in plants. Nevertheless, the importance of exogenous Tre in improving the CS tolerance in rapeseed is still unclear. Therefore, the current study was designed to get mechanistic insights into Tre-mediated CS tolerance in rapeseed seedlings. To explore the Tre role, we designed four treatments [control (CK), CK + 20 mM L-1 Tre, Cold, and Cold + 20 mM L-1 Tre] and three CS conditions (4, 0, and -4°C). The results showed that Tre treatments significantly mitigated the adverse effects of CS on the seedlings and increased the survival rate of Tre-treated seedlings under CS conditions. The exogenous Tre dramatically increased the contents of osmoprotectants, including the soluble sugar (SS), soluble protein (SP), and proline (Pro), and the activities of antioxidant enzymes, such as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were also increased under CS conditions. Additionally, Tre decreased the malondialdehyde (MDA) contents to protect the rapeseed seedlings. Moreover, Tre also remarkably augmented the expression levels of antioxidant genes (CAT12, POD34, and FSD7), CS-responsive marker genes (CBF1, CBF2, CBF4, COR6.6, COR15, COR25, COL1, and KIN1), and Tre-biosynthesis genes (TPS4, TPS8, and TPS9). Briefly, exogenous Tre not only regulates the antioxidant and osmotic balance, but it also significantly participates in Tre metabolism and signaling network to improve the CS tolerance in rapeseed. Thus, Tre-induced supervisory connections between physiological or/and biochemical attributes provide information to dissect the mechanisms of Tre-mediated CS tolerance.

Integrated Analysis of Metabolome and Transcriptome Reveals Insights for Cold Tolerance in Rapeseed (Brassica napus L.).

Rapeseed (Brassica napus L.) is an important oilseed crop in the world. Its productivity is significantly influenced by numerous abiotic stresses, including cold stress (CS). Consequently, enhancement in CS tolerance is becoming an important area for agricultural investigation and crop improvement. Therefore, the current study aimed to identify the stress-responsive genes, metabolites, and metabolic pathways based on a combined transcriptome and metabolome analysis to understand the CS responses and tolerance mechanisms in the cold-tolerant (C18) and cold-sensitive (C6) rapeseed varieties. Based on the metabolome analysis, 31 differentially accumulated metabolites (DAMs) were identified between different comparisons of both varieties at the same time points. From the transcriptome analysis, 2,845, 3,358, and 2,819 differentially expressed genes (DEGs) were detected from the comparison of C6-0 vs. C18-0, C6-1 vs. C18-1, and C6-7 vs. C18-7. By combining the transcriptome and metabolome data sets, we found that numerous DAMs were strongly correlated with several differentially expressed genes (DEGs). A functional enrichment analysis of the DAMs and the correlated DEGs specified that most DEGs and DAMs were mainly enriched in diverse carbohydrates and amino acid metabolisms. Among them, starch and sucrose metabolism and phenylalanine metabolism were significantly enriched and played a vital role in the CS adaption of rapeseed. Six candidate genes were selected from the two pathways for controlling the adaption to low temperature. In a further validation, the T-DNA insertion mutants of their Arabidopsis homologous, including 4cl3, cel5, fruct4, ugp1, axs1, and bam2/9, were characterized and six lines differed significantly in levels of freezing tolerance. The outcome of the current study provided new prospects for the understanding of the molecular basis of CS responses and tolerance mechanisms in rapeseed and present a set of candidate genes for use in improving CS adaptability in the same plant.

Genome-Wide Analysis and Expression Profile of Superoxide Dismutase (SOD) Gene Family in Rapeseed (Brassica napus L.) under Different Hormones and Abiotic Stress Conditions.

Superoxide dismutase (SOD) is an important enzyme that acts as the first line of protection in the plant antioxidant defense system, involved in eliminating reactive oxygen species (ROS) under harsh environmental conditions. Nevertheless, the SOD gene family was yet to be reported in rapeseed (Brassica napus L.). Thus, a genome-wide investigation was carried out to identify the rapeseed SOD genes. The present study recognized 31 BnSOD genes in the rapeseed genome, including 14 BnCSDs, 11 BnFSDs, and six BnMSDs. Phylogenetic analysis revealed that SOD genes from rapeseed and other closely related plant species were clustered into three groups based on the binding domain with high bootstrap values. The systemic analysis exposed that BnSODs experienced segmental duplications. Gene structure and motif analysis specified that most of the BnSOD genes displayed a relatively well-maintained exon-intron and motif configuration within the same group. Moreover, we identified five hormones and four stress- and several light-responsive cis-elements in the promoters of BnSODs. Thirty putative bna-miRNAs from seven families were also predicted, targeting 13 BnSODs. Gene ontology annotation outcomes confirm the BnSODs role under different stress stimuli, cellular oxidant detoxification processes, metal ion binding activities, SOD activity, and different cellular components. Twelve BnSOD genes exhibited higher expression profiles in numerous developmental tissues, i.e., root, leaf, stem, and silique. The qRT-PCR based expression profiling showed that eight genes (BnCSD1, BnCSD3, BnCSD14, BnFSD4, BnFSD5, BnFSD6, BnMSD2, and BnMSD10) were significantly up-regulated under different hormones (ABA, GA, IAA, and KT) and abiotic stress (salinity, cold, waterlogging, and drought) treatments. The predicted 3D structures discovered comparable conserved BnSOD protein structures. In short, our findings deliver a foundation for additional functional investigations on the BnSOD genes in rapeseed breeding programs.

Catalase (CAT) Gene Family in Rapeseed (Brassica napus L.): Genome-Wide Analysis, Identification, and Expression Pattern in Response to Multiple Hormones and Abiotic Stress Conditions.

Catalase (CAT) is an antioxidant enzyme expressed by the CAT gene family and exists in almost all aerobic organisms. Environmental stresses induce the generation of reactive oxygen species (ROS) that eventually hinder plant growth and development. The CAT enzyme translates the hydrogen peroxide (H2O2) to water (H2O) and reduce the ROS levels to shelter the cells' death. So far, the CAT gene family has not been reported in rapeseed (Brassica napus L.). Therefore, a genome-wide comprehensive analysis was conducted to classify the CAT genes in the rapeseed genome. The current study identified 14 BnCAT genes in the rapeseed genome. Based on phylogenetic and synteny analysis, the BnCATs belong to four groups (Groups I-IV). A gene structure and conserved motif analysis showed that Group I, Group II, and Group IV possess almost the same intron/exon pattern, and an equal number of motifs, while Group III contains diverse structures and contain 15 motifs. By analyzing the cis-elements in the promoters, we identified five hormone-correlated responsive elements and four stress-related responsive elements. Further, six putative bna-miRNAs were also identified, targeting three genes (BnCAT4, BnCAT6, and BnCAT8). Gene ontology (GO) enrichment analysis showed that the BnCAT genes were largely related to cellular organelles, ROS response, stimulus response, stress response, and antioxidant enzymes. Almost 10 BnCAT genes showed higher expression levels in different tissues, i.e., root, leaf, stem, and silique. The expression analysis showed that BnCAT1-BnCAT3 and BnCAT11-BnCAT13 were significantly upregulated by cold, salinity, abscisic acid (ABA), and gibberellic acid (GA) treatment, but not by drought and methyl jasmonate (MeJA). Notably, most of the genes were upregulated by waterlogging stress, except BnCAT6, BnCAT9, and BnCAT10. Our results opened new windows for future investigations and provided insights into the CAT family genes in rapeseed.

Omics: The way forward to enhance abiotic stress tolerance in Brassica napus L.

Plant abiotic stresses negative affects growth and development, causing a massive reduction in global agricultural production. Rapeseed (Brassica napus L.) is a major oilseed crop because of its economic value and oilseed production. However, its productivity has been reduced by many environmental adversities. Therefore, it is a prime need to grow rapeseed cultivars, which can withstand numerous abiotic stresses. To understand the various molecular and cellular mechanisms underlying the abiotic stress tolerance and improvement in rapeseed, omics approaches have been extensively employed in recent years. This review summarized the recent advancement in genomics, transcriptomics, proteomics, metabolomics, and their imploration in abiotic stress regulation in rapeseed. Some persisting bottlenecks have been highlighted, demanding proper attention to fully explore the omics tools. Further, the potential prospects of the CRISPR/Cas9 system for genome editing to assist molecular breeding in developing abiotic stress-tolerant rapeseed genotypes have also been explained. In short, the combination of integrated omics, genome editing, and speed breeding can alter rapeseed production worldwide.

Impact of Climate Change on Crops Adaptation and Strategies to Tackle Its Outcome: A Review.

Agriculture and climate change are internally correlated with each other in various aspects, as climate change is the main cause of biotic and abiotic stresses, which have adverse effects on the agriculture of a region. The land and its agriculture are being affected by climate changes in different ways, e.g., variations in annual rainfall, average temperature, heat waves, modifications in weeds, pests or microbes, global change of atmospheric CO2 or ozone level, and fluctuations in sea level. The threat of varying global climate has greatly driven the attention of scientists, as these variations are imparting negative impact on global crop production and compromising food security worldwide. According to some predicted reports, agriculture is considered the most endangered activity adversely affected by climate changes. To date, food security and ecosystem resilience are the most concerning subjects worldwide. Climate-smart agriculture is the only way to lower the negative impact of climate variations on crop adaptation, before it might affect global crop production drastically. In this review paper, we summarize the causes of climate change, stresses produced due to climate change, impacts on crops, modern breeding technologies, and biotechnological strategies to cope with climate change, in order to develop climate resilient crops. Revolutions in genetic engineering techniques can also aid in overcoming food security issues against extreme environmental conditions, by producing transgenic plants.