Study on the differential gene expression of elm leaves fed on by Tetraneura akinire Sasaki.

Abstract

To study the essential molecular mechanism of gall formation is very important. To investigate the differential gene expression in leaves fed on by Tetraneura akinire Sasaki and to provide a basis for the better understanding of the essential molecular mechanism of gall formation. The infected leaves of the elm were divided into three periods: initial formation period (T2), growth and differentiation period (T3), and cracking period (T4). The untouched leaves were used as the control (T1). RNA-Seq was performed, and the high-quality sequences were mapped to the reference genome and the elm gene database to obtain the gene expression profiles. The expression level of each gene was calculated by the RPKM method. A combination of FDR ≤ 0.01 and the absolute value of |log2 ratio (T/CK)| ≥ 2 was used as the threshold to determine the significance of gene expression. Finally, GO and pathway enrichment analyses were used to identify the significantly enriched functional classification and metabolic pathways in DEGs. The results revealed that approximately 244 mRNAs were detected between T1 and T2, including 192 up-regulated and 52 down-regulated mRNAs; approximately 175 mRNAs were detected between T1 and T3, including 145 up-regulated and 30 down-regulated mRNAs; and approximately 372 mRNAs were detected between T1 and T4, including 360 up-regulated and 12 down-regulated mRNAs. Approximately 34 differentially expressed genes were identified by Venn analysis. Comparing the three infection periods to the control, there were 28 up-regulated and six down-regulated mRNAs. Additionally, 562 genes were used for cluster analysis, which revealed that the gene expression in T2 and T3 changed greatly. Genes related to cell proliferation and respiration, such as microtubulin and 6-phosphoric acid fructose kinase were mainly up-regulated during the T2 period. Genes encoding lipoxygenase, glutathione-S-transferase, superoxide dismutase and protease inhibitor were up-regulated during T2 and T3. Genes encoding lignocellulose synthase were up-regulated during T4, which suggests the reinforcement of the cell wall to improve the resistance to the damage of the Tetraneura akinire Sasaki. The results showed that the feeding of Tetraneura akinire Sasaki caused the differential expression of elm genes and influenced cellular energy metabolism. These changes in physiological response and gene expression of the elm compose the physiological and molecular basis of the gall formation and may improve the resistance of elm to Tetraneura akinire Sasaki.