Iron deprivation-induced reactive oxygen species generation leads to non-autolytic PCD in Brassica napus leaves.
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ABSTRACT:
SUBMITTER: Tewari RK
PROVIDER: S-EPMC3661939 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Leaf color is an important characteristic of normal chloroplast development. Variegated plants have green- and white-sectored leaves, which can be used to identify important pathways and molecular mechanisms of chloroplast development. We studied two Brassica napus variegation mutants from same one variegated ancestor, designated ZY-4 and ZY-8, which have different degrees of variegation. When grown in identical conditions, the ratio of white sectors in ZY-4 leaves is higher than in ZY-8. In both mutants, the cells in green sectors contain normal chloroplasts; while, the cells in white sectors contain abnormal plastids. Seedling chloroplasts ultrastructure of both mutants showed that the biogenesis of chloroplasts was blocked in early stages; delayed development and structual damage in ZY-4 were more serious than in ZY-8. Employing bulked segregant analysis(BSA), two bulks (BY142 and BY137) from BC2F1 lines derived from ZY-4 and ZS11, and one bulk (BY56) from BC2F1 lines derived from ZY-8 and ZS11, and screening by Brassica 60K SNP BeadChip Array, showed the candidate regions localized in chromosome A08 (BY142), C04 (BY137), and A08 (BY56), respectively. Transcriptome analysis of five seedling development stages of ZY-4, ZY-8, and ZS11 showed that photosynthesis, energy metabolism-related pathways and translation-related pathways were important for chloroplast biogenesis. The number of down- or up-regulated genes related to immune system process in ZY-4 was more than in ZY-8. The retrograde signaling pathway was mis-regulated in both mutants. DEG analysis indicated that both mutants showed photooxidative damages. By coupling transcriptome and BSA CHIP analyses, some candidate genes were identified. The gene expression pattern of carotene biosynthesis pathway was disrupted in both mutants. However, histochemical analysis of ROS revealed that there was no excessive accumulation of ROS in ZY-4 and ZY-8. Taken together, our data indicate that the disruption of carotene biosynthetic pathways leads to the variegation phenotypes of ZY-4 and ZY-8 and there are some functions that can compensate for the disruption of carotene biosynthesis in ZY-4 and ZY-8 to reduce ROS and prevent seedling mortality.
| S-EPMC7297816 | biostudies-literature
Project description:Iron toxicity is a nutrient disorder that severely affects crop development and yield in some soil conditions. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT) members are involved in this process and play essential roles in iron storage and transport. In this study, we identified a rapeseed VIT gene BnMEB2 (BnaC07g30170D) homologs to Arabidopsis MEB2 (At5g24290). Transient expression analysis revealed that BnMEB2 was localized to the vacuolar membrane. Q-PCR detection showed a high expression of BnMEB2 in mature (60-day-old) leaves and could be obviously induced by exogenous iron stress in both roots and leaves. Over-expressed BnMEB2 in both Arabidopsis wild type and meb2 mutant seedlings resulted in greatly improved iron tolerability with no significant changes in the expression level of other VIT genes. The mutant meb2 grew slowly and its root hair elongation was inhibited under high iron concentration condition while BnMEB2 over-expressed transgenic plants of the mutant restored the phenotypes with apparently higher iron storage in roots and dramatically increased iron content in the whole plant. Taken together, these results suggested that BnMEB2 was a VIT gene in rapeseed which was necessary for safe storage and vacuole detoxification function of excess iron to enhance the tolerance of iron toxicity. This research sheds light on a potentially new strategy for attenuating hazardous metal stress from environment and improving iron biofortification in Brassicaceae crops.
| S-EPMC5020681 | biostudies-literature
Project description:The role of phosphatidylcholine (PC) in fatty acid exchange and desaturation was examined and compared with that of monogalactosyldiacylglycerol (MGDG) in Brassica napus leaves using (14)C-labelling in vivo. Data are presented which indicate that in the chloroplast newly formed saturated (palmitic acid, 16:0) and monounsaturated (oleic acid, 18:1) fatty acid is incorporated into MGDG and desaturated in situ. In the non-plastidic compartments, however, newly formed fatty acid is exchanged with polyunsaturated fatty acid in PC, the probable major site of subsequent desaturation. The unsaturated fatty acid is released to the acyl-CoA pool, which is then used to synthesize diacylglycerol (DAG) containing a high level of unsaturated fatty acid. This highly unsaturated DAG may be the source for the biosynthesis of other cellular glycerolipids. The generally accepted pathway in which PC is synthesized from molecular species of DAG containing 16:0 and 18:1 followed by desaturation of the 18:1 to linoleic (18:2) and linolenic (18:3) acids is questioned.
| S-EPMC1221129 | biostudies-other
Project description:Salt stress limits plant growth and crop productivity and is an increasing threat to agriculture worldwide. In this study, proteomic and physiological responses of Brassica napus leaves under salt stress were investigated. Seedlings under salt treatment showed growth inhibition and photosynthesis reduction. A comparative proteomic analysis of seedling leaves exposed to 200 mM NaCl for 24 h, 48 h and 72 h was conducted. Forty-four protein spots were differentially accumulated upon NaCl treatment and 42 of them were identified, including several novel salt-responsive proteins. To determine the functional roles of these proteins in salt adaptation, their dynamic changes in abundance were analyzed. The results suggested that the up-accumulated proteins, which were associated with protein metabolism, damage repair and defense response, might contribute to the alleviation of the deleterious effect of salt stress on chlorophyll biosynthesis, photosynthesis, energy synthesis and respiration in Brassica napus leaves. This study will lead to a better understanding of the molecular basis of salt stress adaptation in Brassica napus and provides a basis for genetic engineering of plants with improved salt tolerance in the future.
| S-EPMC4686907 | biostudies-literature
Project description:The essential pigment chlorophyll (Chl) plays important roles in light harvesting and energy transfer during photosynthesis. Here we present the data from a comparative proteomic analysis of chlorophyll-deficient Brassica napus mutant cde1 and its corresponding wild-type using the iTRAQ approach (Pu Chu et al., 2014 [1]). The distribution of length and number of peptides, mass and sequence coverage of proteins identified was calculated, and the repeatability of the replicates was analyzed. A total of 443 differentially expressed proteins were identified in B. napus leaves, including 228 down-accumulated proteins mainly involved in photosynthesis, porphyrin and chlorophyll metabolism, biosynthesis of secondary metabolites, carbon fixation and 215 up-accumulated proteins that enriched in the spliceosome, mRNA surveillance and RNA degradation.
| S-EPMC4459558 | biostudies-other
Project description:Potassium (K) plays a crucial role in plant growth and development and is involved in different physiological and biochemical functions in plants. Brassica napus needs higher amount of nutrients like nitrogen (N), K, phosphorus (P), sulfur (S), and boron (B) than cereal crops. Previous studies in B. napus are mainly focused on the role of N and S or combined deficiencies. Hence, little is known about the response of B. napus to K deficiency. Here, a physiological, biochemical, and molecular analysis led us to investigate the response of hydroponically grown B. napus plants to K deficiency. The results showed that B. napus was highly sensitive to the lack of K. The lower uptake and translocation of K induced BnaHAK5 expression and significantly declined the growth of B. napus after 14 days of K starvation. The lower availability of K was associated with a decrease in the concentration of both S and N and modulated the genes involved in their uptake and transport. In addition, the lack of K induced an increase in Ca2+ and Mg2+ concentration which led partially to the accumulation of positive charge. Moreover, a decrease in the level of arginine as a positively charged amino acid was observed which was correlated with a substantial increase in the polyamine, putrescine (Put). Furthermore, K deficiency induced the expression of BnaNCED3 as a key gene in abscisic acid (ABA) biosynthetic pathway which was associated with an increase in the levels of ABA. Our findings provided a better understanding of the response of B. napus to K starvation and will be useful for considering the importance of K nutrition in this crop.
| S-EPMC8409508 | biostudies-literature
Project description:Brassica napus seed is a lipid storage organ containing approximately 40% oil, while its leaves contain many kinds of lipids for many biological roles, but the overall amounts are less than in seeds. Thus, lipid biosynthesis in the developing seeds and the leaves is strictly regulated which results the final difference of lipids. However, there are few reports about the molecular mechanism controlling the difference in lipid biosynthesis between developing seeds and leaves. In this study, we tried to uncover this mechanism by analyzing the transcriptome data for lipid biosynthesis. The transcriptome data were de novo assembled and a total of 47,216 unigenes were obtained, which had an N50 length and median of 1271 and 755 bp, respectively. Among these unigenes, 36,368 (about 77.02%) were annotated and there were 109 up-regulated unigenes and 72 down-regulated unigenes in the developing seeds lipid synthetic pathway after comparing with leaves. In the oleic acid pathway, 23 unigenes were up-regulated and four unigenes were down-regulated. During triacylglycerol (TAG) synthesis, the key unigenes were all up-regulated, such as phosphatidate phosphatase and diacylglycerol O-acyltransferase. During palmitic acid, palmitoleic acid, stearic acid, linoleic acid and linolenic acid synthesis in leaves, the unigenes were nearly all up-regulated, which indicated that the biosynthesis of these particular fatty acids were more important in leaves. In the developing seeds, almost all the unigenes in the ABI3VP1, RKD, CPP, E2F-DP, GRF, JUMONJI, MYB-related, PHD and REM transcript factor families were up-regulated, which helped us to discern the regulation mechanism underlying lipid biosynthesis. The differential up/down-regulation of the genes and TFs involved in lipid biosynthesis in developing seeds and leaves provided direct evidence that allowed us to map the network that regulates lipid biosynthesis, and the identification of new TFs that are up-regulated in developing seeds will help us to further elucidate the lipids biosynthesis pathway in developing seeds and leaves.
| S-EPMC4429122 | biostudies-literature
Project description:In the spring oilseed rape (OSR) cultivar 'Mozart' grown under optimal N supply (NO) or mild N deficiency (NL) the transcriptome changes associated with progressing age until early senescence in developmentally old lower canopy leaves (leaf #4) and younger higher canopy leaves (leaf #8) were investigated. Twelve weeks old NO and NL plants appeared phenotypically and transcriptomically identical, but thereafter distinct nutrition-dependent differences in gene expression patterns in lower and upper canopy leaves emerged. In NO leaves #4 of 14-week-old compared to 13-week-old plants, ?600 genes were up- or downregulated, whereas in NL leaves #4 ?3000 genes were up- or downregulated. In contrast, in 15-week-old compared to 13-week-old upper canopy leaves #8 more genes were up- or downregulated in optimally N-supplied plants (?2000 genes) than in N-depleted plants (?750 genes). This opposing effect of N depletion on gene regulation was even more prominent among photosynthesis-related genes (PSGs). Between week 13 and 14 in leaves #4, 99 of 110 PSGs were downregulated in NL plants, but none in NO plants. In contrast, from weeks 13 to 16 in leaves #8 of NL plants only 11 PSGs were downregulated in comparison to 66 PSGs in NO plants. Different effects of N depletion in lower versus upper canopy leaves were also apparent in upregulation of autophagy genes and NAC transcription factors. More than half of the regulated NAC and WRKY transcription factor, autophagy and protease genes were specifically regulated in NL leaves #4 or NO leaves #8 and thus may contribute to differences in senescence and nutrient mobilization in these leaves. We suggest that in N-deficient plants the upper leaves retain their N resources longer than in amply fertilized plants and remobilize them only after shedding of the lower leaves.
| S-EPMC5799827 | biostudies-literature
Project description:BackgroundMost studies of photosynthesis in chlorenchymas under potassium (K) deficiency focus exclusively on leaves; however, little information is available on the physiological role of K on reproductive structures, which play a critical role in plant carbon gain. Brassica napus L., a natural organ-succession species, was used to compare the morphological, anatomical and photo-physiological differences between leaves and siliques exposed to K-deficiency.ResultsCompared to leaves, siliques displayed considerably lower CO2 assimilation rates (A) under K-deficient (-K) or sufficient conditions (+K), limited by decreased stomatal conductance (g s), apparent quantum yield (α) and carboxylation efficiency (CE), as well as the ratio of the maximum rate of electron transport (J max) and the maximum rate of ribulose 1,5-bisphosphate (RuBP) carboxylation (V cmax). The estimated J max, V cmax and α of siliques were considerably lower than the theoretical value calculated on the basis of a similar ratio between these parameters and chlorophyll concentration (i.e. J max/Chl, V cmax/Chl and α/Chl) to leaves, of which the gaps between estimated- and theoretical-J max was the largest. In addition, the average ratio of J max to V cmax was 16.1% lower than that of leaves, indicating that the weakened electron transport was insufficient to meet the requirements for carbon assimilation. Siliques contained larger but fewer stoma, tightly packed cross-section with larger cells and fewer intercellular air spaces, fewer and smaller chloroplasts and thin grana lamellae, which might be linked to the reduction in light capture and CO2 diffusion. K-deficiency significantly decreased leaf and silique A under the combination of down-regulated stomatal size and g s, chloroplast number, α, V cmax and J max, while the CO2 diffusion distance between chloroplast and cell wall (D chl-cw) was enhanced. Siliques were more sensitive than leaves to K-starvation, exhibiting smaller reductions in tissue K and parameters such as g s, V cmax, J max and D chl-cw.ConclusionSiliques had substantially smaller A than leaves, which was attributed to less efficient functioning of the photosynthetic apparatus, especially the integrated limitations of biochemical processes (J max and V cmax) and α; however, siliques were slightly less sensitive to K deficiency.
| S-EPMC5725657 | biostudies-literature
Project description:Leaf senescence is a long developmental process important for nutrient management and for source to sink remobilization. Constituents of the mesophyll cells are progressively degraded to provide nutrients to the rest of the plant. Up to now, studies on leaf senescence have not paid much attention to the role of the different leaf tissues. In the present study, we dissected leaf laminae from the midvein to perform metabolite profiling. The laminae mesophyll cells are the source of nutrients, and in C3 plants they contain Rubisco as the most important nitrogen storage pool. Veins, rich in vasculature, are the place where all the nutrients are translocated, and sometimes interconverted, before being exported through the phloem or the xylem. The different metabolic changes we observed in laminae and midvein with ageing support the idea that the senescence programme in these two tissues is different. Important accumulations of metabolites in the midvein suggest that nutrient translocations from source leaves to sinks are mainly controlled at this level. Carbon and nitrogen long-distance molecules such as fructose, glucose, aspartate, and asparagine were more abundant in the midvein than in laminae. In contrast, sucrose, glutamate, and aspartate were more abundant in laminae. The concentrations of tricarboxylic acid (TCA) compounds were also lower in the midvein than in laminae. Since nitrogen remobilization increased under low nitrate supply, plants were grown under two nitrate concentrations. The results revealed that the senescence-related differences were mostly similar under low and high nitrate conditions except for some pathways such as the TCA cycle.
| S-EPMC5853214 | biostudies-literature