Transcriptome analysis the citrus rootstocks of Ziyang xiangcheng (Citrus junos Sieb.) and Poncirus trifoliate (Poncirus trifoliata (L.) Raf.) under saline-alkali stress
Salt stress, especially saline-alkali stress, has seriously negative effect on citrus production. Ziyang xiangcheng (Citrus junos Sieb.) (Cj) has been reported as a saline-alkali stress and iron deficiency tolerant citrus rootstock. However, the molecular mechanism of its saline-alkali stress tolerance is still not clear. Two citrus rootstocks and one navel orange scion, Cj, Poncirus trifoliate (Poncirus trifoliata (L.) Raf.) (Pt) and 'Lane Late' navel orange (Citrus sinensis (L.) Osb.) (LL), were used in this study. The grafted materials Cj+LL and Pt+LL grown in calcareous soil were used to identify genes and pathways responsive to saline-alkali stress using RNA-seq. The seedlings of Cj and Pt grown in the solutions with different gradient pH value were used to perform a supplement experiment. Comprehensively analyzing the data of RNA-seq, physiology and biochemistry, agronomic traits and mineral elements of Cj+LL, Pt+LL, Cj and Pt, several candidate pathways and genes were identified to be highly regulated under saline-alkali stress. Here, we propose citrate is important for the tolerance to iron deficiency and the jasmonate (JA) biosynthesis and signal transduction pathway may play a crucial role in tolerance to saline-alkali stress in citrus by interacting with other plant hormones, calcium signaling, ROS scavenging system and lignin biosynthesis. Overall design: Two citrus rootstocks, Ziyang xiangcheng (Citrus junos Sieb.) (Cj) and Poncirus trifoliate (Poncirus trifoliata (L.) Raf.) (Pt), one navel orange scion, 'Lane Late' navel orange (Citrus sinensis (L.) Osb.) (LL), were used in this study. LL was grafted on Cj and Pt, respectively. The grafted materials Cj+LL and Pt+LL (rootstock+scion) were planted in the same orchard in 2009, which was located in Changyang city, Hubei province, China. The root, stem and leaf samples of Cj+LL and Pt+LL were subjected to RNA-seq using BGISEQ-500 at Beijing Genomics Institute (Shenzhen) in 2015. Each sample performed two biological replicates.