Physiological Response And Transcriptome Analysis Of Roots Of Cowpea Seedlings Under Exogenous Cinnamic Acid Stress

Cowpea is an important legume vegetable,which is widely planted all over the world.With the development of agriculture,the problem of continuous cropping obstacle becomes more and more obvious in some vegetable industrialization production because cowpea is planted all year.Because autotoxicity is the main reason of continuous cropping obstacle and cinnamic acid is the main autotoxicity of cowpea,it is very meaningful to explore the mechanism of cinnamic acid toxicity to cowpea.In order to explore the effect of cinnamic acid on roots of cowpea,two different sensitivity to autotoxicity varieties cowpea TZ30and ZQJ6 were used to treat with 0.2 mmol·L^-1 cinnamic acid under the condition of hydroponics,and the physiological and biochemical indexes of the roots were measured and analyzed and transcriptome analysis was followed.The results were as follows:1.Cinnamic acid treatment had obvious toxic effects on both cowpeas,the total root length,total root surface area,total root volume,and total root tips number of the two cowpea species were significantly decreased by cinnamic acid treatment,TZ30 show less decrease,reflecting lower sensitivity of TZ30.The mean root diameter of TZ30 increased without significant difference,the mean root diameter of ZQJ6 increased with significant difference,reflecting lower sensitivity of TZ30,which indicated that the influence of cinnamic acid on cowpea roots was mainly in young roots.The activity of superoxide dismutase（SOD）,peroxidase（POD）and ascorbate peroxidase（APX）on roots of the two kinds of cowpea were increased significantly,explain that cowpea resistance the effect of cinnamic acid by increasing the activity of antioxidant enzymes,the activity of antioxidant enzymes of TZ30 improve higher than ZQJ6,explain cinnamic acid resistivity of TZ30 is higher than ZQJ6.Both varieties of cowpea showed significant increase in relative electrical conductivity and significant decrease in soluble protein content,indicating that cinnamic acid destroyed cell structure of cowpea root system.Among them,TZ30 root system showed more increase in relative electrical conductivity and more decrease in soluble protein than ZQJ6,indicating that TZ30 cell structure suffered more serious damage.2.Transcriptome sequencing and bioinformatics analysis of the root systems of two kinds of cowpea under cinnamic acid stress revealed that a total of 382365 Ugenes were obtained by clustering.After the statistical analysis and comparison of the gene expression of two kinds of cowpea,it was found that after the stress of 0.2mmol·L^-1 cinnamic acid,31691 cinnamic acid responsive genes were identified in the cowpea lower sensitivity varieties TZ30,among which 17514 were up-regulated and 14117 were down-regulated.In cowpea higher sensitive varieties ZQJ6,18898 cinnamic acid responsive differentially expressed genes were identified,with 13157 up-regulated and 5741 down-regulated.Among the differentially expressed genes of the two varieties cowpea,8697 differentially expressed genes were co-expressed,among which 6371 were up-regulated,2262 were down-regulated,31 were up-regulated in TZ30,down-regulated in ZQJ6,and 33 were down-regulated in TZ30 and up-regulated in ZQJ6.Functional annotation and enrichment analysis were performed for these differentially expressed genes in the databases of GO and KEGG.GO annotation results showed that the differentially expressed genes of TZ30were mainly enriched in oxidation-reduction process and regulation of transcription,DNA-templated and some other subclasses.ZQJ6 differentially expressed genes were mainly enriched in organic substance biosynthetic process,cellular nitrogen compound metabolic process and some other subclasses.The enrichment analysis of KEGG pathway showed that the differentially expressed genes of TZ30 were mainly enriched in the protein processing in endoplasmic reticulum,the plant-pathogen interaction and some other pathways.ZQJ6 differentially expressed genes are mainly enriched in Starch and sucrose metabolism,biosynthesis of amino acid and some other pathways.Combined the results of this study with previous research results,64 candidate genes in response to cinnamic acid stress were screened out,among which Protein ROS1,proline-rich protein and some other genes were related to the stress effect;Fasciclin-like arabinogalactan protein and 60S acidic ribosomal protein P0 and some other genes were correlated with plant growth and metabolism;Receptor-like protein kinase FERONIA,Somatic embryogenesis receptor kinase and some other genes were correlated with hormones;Leucine-rich repeat receptor-like serine/threonine-protein kinase,Pentatricopeptide repeat-containing protein and some other genes were correlated with signal transmission.These genes are related candidate genes for the sensitivity of cowpea to cinnamic acid autotoxicity,which can provide some theoretical references for the screening of cowpea varieties with low sensitivity to cowpea autotoxicity and the cultivation of cowpea varieties with low sensitivity to cowpea autotoxicity.