Project description: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.
Project description:MicroRNAs (miRNAs) play a critical role in post-transcriptional gene regulation. miRNAs have been shown to control many genes involved in various biological and metabolic processes. Deep sequencing technologies have facilitated identification of species-specific or lowly expressed as well as conserved or highly expressed miRNAs in plants. In this research, we used Solexa sequencing to discover new microRNAs in trifoliate orange (Citrus trifoliata) an important rootstock of citrus. A total of 13,106,753 reads representing 4,876,395 distinct sequences were obtained from a short RNA library generated from small RNA extracted from C. trifoliata flower and fruit tissues, Based on sequence similarity and hairpin structure prediction, we found that 178,102 reads representing 89 sequences from 42 highly conserved miRNA families, have perfect matches to known miRNAs. We also identified 10 novel miRNA candidates, whose precursors were all potentially generated from citrus ESTs. And of them five miRNA* sequences were also sequenced. These sequences had not been described in other plant species and accumulation of these 10 novel miRNAs were confirmed by qRT-PCR analysis. Potential target genes were predicted for most conserved and novel miRNAs. Moreover, four target genes included one encoding IRX12 copper ion binding/ oxidoreductase and three genes encoding NB-LRR disease resistance protein have been experimentally verified by detection of the miRNA-mediated mRNA cleavage in C. trifoliata.
