Plant growth and development are significantly affected by salt stress. Chrysanthemum lavandulifolium is a halophyte species and one of the ancestors of chrysanthemum (C. ×morifolium). Understanding how this species tolerates salt stress could provide vital insight for clarifying the salt response systems of higher plants, and chrysanthemum-breeding programs could be improved. In this study, salt tolerance was compared among C. lavandulifolium and three chrysanthemum cultivars by physiological experiments, among which C. lavandulifolium and Jinba displayed better tolerance to salt stress than the other two cultivars, whereas Xueshan was a salt-sensitive cultivar. Using the transcriptome database of C. lavandulifolium as a reference, we used digital gene expression technology to analyze the global gene expression changes in C. lavandulifolium seedlings treated with 200 mm NaCl for 12 hours compared with seedlings cultured in normal conditions. In total, 2254 differentially expressed genes (DEGs), including 1418 up-regulated and 836 down-regulated genes, were identified. These DEGs were significantly enriched in 35 gene ontology terms and 29 Kyoto Encyclopedia of Genes and Genomes pathways. Genes related to signal transduction, ion transport, proline biosynthesis, reactive oxygen species scavenging systems, and flavonoid biosynthesis pathways were relevant to the salt tolerance of C. lavandulifolium. Furthermore, comparative gene expression analysis was conducted using reverse transcription polymerase chain reaction to compare the transcriptional levels of significantly up-regulated DEGs in C. lavandulifolium and the salt-sensitive cultivar Xueshan, and species-specific differences were observed. The analysis of one of the DEGs, ClAKT, an important K+ transport gene, was found to enable transgenic Arabidopsis thaliana to absorb K+ and efflux Na+ under salt stress and to absorb K+ under drought stress. The present study investigated potential genes and pathways involved in salt tolerance in C. lavandulifolium and provided a hereditary resource for the confinement of genes and pathways responsible for salt tolerance in this species. This study provided a valuable source of reference genes for chrysanthemum cultivar transgenesis breeding.
He Huang, Yuting Liu, Ya Pu, Mi Zhang and Silan Dai
Yuting Meng, Boling Liu, Ping Zhang, Ping Cui, Yuguang Song, Nianwei Qiu, Guoliang Han and Feng Zhou
2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) is one of the most toxic polybrominated diphenyl ethers (PBDEs). The toxic effects of BDE-47 on Chinese cabbage seedlings were analyzed in this study. After a 30-day hydroponic exposure to BDE-47 at different concentrations (25, 50, 75, and 100 µg·L−1), the fresh weight of Chinese cabbage seedlings was significantly decreased, whereas their root:shoot ratio was increased, indicating that BDE-47 inhibited the growth of the plant, especially the overground parts. The water content, chlorophyll content, and protein content of Chinese cabbage leaves also markedly decreased with the increase of the BDE-47 concentration. In addition, BDE-47 weakened the photosynthetic capacity of the leaves, which was supported by the decreased photosynthetic parameters [net photosynthetic rate (P n) and stomatal conductance (g S)]. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves were enhanced after exposure to BDE-47, the increased malondialdehyde (MDA) content attested to the existence of membrane lipid peroxidation. The increased plasma membrane permeability and the decreased chlorophyll fluorescence parameters [the maximum quantum yield of PSII photochemistry at t = 0 (F v/F m), photosystem II (PSII) reaction centers (RCs) per cross section (CS) (RC/CS), absorption energy flux per CS (ABS/CS), trapped energy flux per CS (TR o/CS), electron transport flux per CS (ET o/CS), performance index on the absorption basis (PI abs), and driving force for photosynthesis (DF)] further proved that the plasma membrane and photosynthetic membrane were damaged by BDE-47. Our study demonstrated the phytotoxicities of BDE-47 to Chinese cabbage, which can provide valuable information for understanding the toxicity of BDE-47 on vegetables.