Transcriptome analysis for Fraxinus mandshurica seedlings from different carbon fixation and growth provenances in response to nitrogen deficiency

Background The carbon fixation characteristic of F. mandshurica seedlings from 20 provenances has been evaluated by our research group. In order to explore whether growth and carbon sequestration are related to nutritional adaptability, the foliage and roots of the annual Wuchang (WC) seedlings with high carbon content and Hailin (HL) seedlings with low carbon content which were grown in nitrogen-deficient nutrition and total nutrition were used for RNA-seq determination. Results Eight transcriptome libraries by high-throughput sequence were analysis. 1,235,174,984 clean reads and 88,655 unigenes with N50 length of 1,259 bp were obtained. Under normal nitrogen condition, 783 differentially expressed genes (DEGs) between WC and HL were identified, the number in foliage (669) of DEGs between HL and WC was more than that in roots (149). The number of transcription factors (TFs), hormone, and Protein kinase (PK) genes was significantly more in WC than that in HL. Compared to the normal nitrogen, 8173 DEGs related to nitrogen deficiency were identified and the number of DEGs in roots (6999) was more than that in foliage (1616). Several nitrogen deficiency-related metabolic pathways and many DEGs involved in nitrogen absorption and assimilation, carbon metabolism, hormones, transcription factors and kinases were identified. The numbers of DEGs encoding nitrate transporters, PK, TFs and hormone in WC were less than that in HL, which indicated the response of HL provenance seedlings to nitrogen deficiency was stronger than that of WC provenance seedlings. However, under nitrogen deficiency, the number of up-regulated DEGs in the WC provenance seedlings is more than that in the HL, which indicated that the WC provenance seedlings were more tolerant to nitrogen deficiency than HL. Conclusions The data showed that high carbon content and high growth rate of WC provenance seedlings are mainly attributed to the high transcriptional expression of many metabolic genes in foliage. The response of HL provenance seedlings to nitrogen deficiency is significantly greater than that of WC provenances seedlings, but WC provenance seedlings were more tolerant to nitrogen deficiency than HL. Many genes related to nitrogen deficiency were identified, which will expand our current understanding of nitrogen responses.