Abstract
BackgroundVery little is known about manganese (Mn)-toxicity-responsive genes in citrus plants. Seedlings of ‘Xuegan’ (Citrus sinensis) and ‘Sour pummelo’ (Citrus grandis) were irrigated for 17 weeks with nutrient solution containing 2 μM (control) or 600 μM (Mn-toxicity) MnSO4. The objectives of this study were to understand the mechanisms of citrus Mn-tolerance and to identify differentially expressed genes, which might be involved in Mn-tolerance.ResultsUnder Mn-toxicity, the majority of Mn in seedlings was retained in the roots; C. sinensis seedlings accumulated more Mn in roots and less Mn in shoots (leaves) than C. grandis ones and Mn concentration was lower in Mn-toxicity C. sinensis leaves compared to Mn-toxicity C. grandis ones. Mn-toxicity affected C. grandis seedling growth, leaf CO2 assimilation, total soluble concentration, phosphorus (P) and magenisum (Mg) more than C. sinensis. Using cDNA-AFLP, we isolated 42 up-regulated and 80 down-regulated genes in Mn-toxicity C. grandis leaves. They were grouped into the following functional categories: biological regulation and signal transduction, carbohydrate and energy metabolism, nucleic acid metabolism, protein metabolism, lipid metabolism, cell wall metabolism, stress responses and cell transport. However, only 7 up-regulated and 8 down-regulated genes were identified in Mn-toxicity C. sinensis ones. The responses of C. grandis leaves to Mn-toxicity might include following several aspects: (1) accelerating leaf senescence; (2) activating the metabolic pathway related to ATPase synthesis and reducing power production; (3) decreasing cell transport; (4) inhibiting protein and nucleic acid metabolisms; (5) impairing the formation of cell wall; and (6) triggering multiple signal transduction pathways. We also identified many new Mn-toxicity-responsive genes involved in biological and signal transduction, carbohydrate and protein metabolisms, stress responses and cell transport.ConclusionsOur results demonstrated that C. sinensis was more tolerant to Mn-toxicity than C. grandis, and that Mn-toxicity affected gene expression far less in C. sinensis leaves. This might be associated with more Mn accumulation in roots and less Mn accumulation in leaves of Mn-toxicity C. sinensis seedlings than those of C. grandis seedlings. Our findings increase our understanding of the molecular mechanisms involved in the responses of plants to Mn-toxicity.
Highlights
Very little is known about manganese (Mn)-toxicity-responsive genes in citrus plants
Root dry weight (DW), whole plant DW and the ratio of root DW to shoot DW were higher in C. sinensis seedlings than in C. grandis ones or similar between two species, except that shoot DW was lower in the former at the 2 μM Mn treatment (Figure 1)
A few C. grandis leaves from the minority of Mn-toxicity plants became interveinal chlorosis or necrotic blotching of foliage, while no visible symptoms occurred in Mn-toxicity C. sinensis leaves (Additional file 1)
Summary
Very little is known about manganese (Mn)-toxicity-responsive genes in citrus plants. The objectives of this study were to understand the mechanisms of citrus Mn-tolerance and to identify differentially expressed genes, which might be involved in Mn-tolerance. Manganese (Mn), which is the twelfth abundant element and the third most common element in the Earth’s crust, is absorbed mainly as Mn2+ by plant roots [1]. An essential trace element for the normal growth and development of higher plant, is involved in many biochemical processes. With decreasing pH, the amount of exchangeable Mn (mainly Mn2+ form) increases in the soil solution [2]. After aluminum (Al), Mn-toxicity is probably the most important factor limiting plant productivity in acidic soils, which comprise up to 50% of the world’s potentially arable lands [5]. The acidity of the soils is gradually increasing due to rapid industrialization, the emission of acidic gases and acid deposition [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
