Effects Of Elevated CO₂ Concentration And Warming On Maize Photosynthetic Carbon Distribution And Community Of Rhizosphere Bacterial

Warming and elevated CO₂concentration?e CO₂?may affect the photosynthetic carbon input into soil and the transformation of soil organic carbon,which would inevitably affect the stability of soil carbon pool,but the magnitude of this effect may depend on the soil type.However,the interactive effect of warming and e CO₂ on the soil quality and productivity of corn belt has not yet been assessed.This requires an integrative study on plant transcriptome manipulating physiological functions,plant growth and productivity under climate change,and the photosynthetic carbon distribution to soil organic carbon pools and the relevant changes of microbial community characteristics in different soils.This study provides the data for the prediction of the impact of global climate change on carbon cycle in corn farming ecosystem and evidence on the influence of climate change on maize yield,which would be helpful to the management of soil organic carbon and the maintenance of productivity in future maize producing areas.The study investigated the effects of warming and e CO₂on different soils carbon pools and the related microbiological mechanism.Exploring the transcriptome of crops in response to warming and e CO₂ is important togaining insights of botanical adaption and feedback to climate change.This study deployed Illumina sequencing technology to characterize transcriptomic profile of maize plants,which were grown under warmingand e CO₂ conditions.Thus,we analyzed the effects of climate change on the regulation of physiological function gene expression.The soil was collected from the tillage layer of 0–10 cm depth from4 major maize-growing soils,i.e.Phaeozem,Fluvisol,Kastanozem and Acrisol.This study targeted on the effects of warming and e CO₂ on photosynthetic carbon distribution in different farming soils and relevant mechanisms by isotope labeling technique.We analyzed the photosynthetic carbon in soil carbon pools,and revealed organic carbon contents in different organic carbon fractions in response to warming and e CO₂.Illumina sequencing technology was used to analyze the response of soil bacterial community structures to warming and e CO₂.The results were as follows:1.Warming,e CO₂ and warming plus e CO₂ resulted in 2732,1966 and 271 genes expressing differently?DEGs?compared to CK,respectively.Elevated CO₂significantly inhibited gene expressions in terms of photosynthesis and carbohydrate biosynthesis pathways.Warming not only negatively suppressed the expression of these above genes,but also secondary pathways of nitrogen?N?metabolism.These results indicated the negative effect of warming and e CO₂on some physiological and biochemical functions in maize might occur,highlighting the necessity to improve the genetic adaptability of plant to future climate change.2.The distribution of photosynthetic carbon in different soils at the silking stage of maize under warming and e CO₂were investigated with the ¹³C labeling technique.The proportion of ¹³C tothe total fixed ¹³C increased by 44.6%,96.1%and 41.9%in Phaeozem under warming,e CO₂ and warming plus e CO₂ treatments compared with control,while decreased in Fluvisol,Kastanozem and Acrisol in response to either e CO₂,warming and warming plus e CO₂.3.The proportion of ¹³C tothe total fixed ¹³C was the highest in maize stem,leaf and grain,accounting for 17.3%-23.3%and 21.7%-25.8%,respectively,following by the root?3.15%-4.81%?,and soil?1.20%-1.61%?.During the whole growth period,the loss of photosynthetic carbon was approximately 50%.Elevated CO₂increased the distribution of photosynthetic carbon in stem,leaf,grain,root and soil.Except the photosynthetic carbon distribution to root decreased under warming,the photosynthetic carbon distribution in other plant parts were not affected.Warming plus CO₂significantly increased the photosynthetic carbon distribution to stem,leaf and grain,while had no effect in root and soil.4.The e CO₂treatment significantly increased the carbon content by 60%in the fine particle organic carbon.Warming plus e CO₂significantly increased the carbon content in the coarse particle organic carbon,which might be mainly from the photosynthetic carbon.Although e CO₂increased the photosynthetic carbon content in mineral-associated organic carbon?MOC?,it did not affect the carbon content of MOC components.5.The dominant phyla of microorganisms in the four soils were Actinobacteria,Proteobacteria,Chloroflexi and Acidobacteria.Different soil types had significant effects on microbial community composition.Warming had a significant effect on the OTU number in Phaeozem.Warming increased the OTU number in Streptomyces and decreased the OTU number in Sphingomonas.OTU numbers in Ilumatobacter and Gaiella affiliated to Fluvisol were significantly reduced by e CO₂,while OTU numbers in Pseudarthrobacter,Gaiella and Shinella in Kastanozem were all affected by e CO₂,but the trend was inconsistent.OTU numbers in Gaiellales?norank,Pseudonocardia,Acidothermus and Xanthobacteraceae?norank affiliated to Acrisol were significantly affected by e CO₂.Warming plus e CO₂significantly affected the OTU number in Rhodospirillaceae?norank affiliated to Fluvisol,the OTU number in Shinella affiliated to Kastanozem and the OTU number in Gaiellales?norank,Streptomyces and Acidothermus affiliated to Acrisol.