Bacterial wilt caused by Ralstonia solanacearum is a serious soil-borne disease of peanut (Arachis hypogaea L). The molecular basis of peanut response to R. solanacearum remains unknown. To understand the resistance mechanism behind peanut resistance to R. solanacearum, we used RNA-Seq to perform global transcriptome profiling on the roots of peanut resistant (R) and susceptible (S) genotypes under R. solanacearum infection.

Soil salinity is a main abiotic stress in agriculture worldwide. The Na⁺/H⁺ antiporters (NHXs) play pivotal roles in intracellular Na⁺ excretion and vacuolar Na⁺ compartmentalization, which are important for plant salt stress resistance (SSR). However, few systematic analyses of NHXs has been reported in allotetraploid rapeseed so far. Here, a total of 18 full-length NHX homologs, representing seven subgroups (NHX1-NHX8 without NHX5), were identified in the rapeseed genome (A_nA_nC_nC_n). Number variations of BnaNHXs might indicate their significantly differential roles in the regulation of rapeseed SSR. BnaNHXs were phylogenetically divided into three evolutionary clades, and the members in the same subgroups had similar physiochemical characteristics, gene/protein structures, and conserved Na⁺ transport motifs. Darwin´s evolutionary pressure analysis suggested that BnaNHXs suffered from strong purifying selection. The cis-element analysis revealed the differential transcriptional regulation of NHXs between the model Arabidopsis and B. napus. Differential expression of BnaNHXs under salt stress, different nitrogen forms (ammonium and nitrate), and low phosphate indicated their potential involvement in the regulation of rapeseed SSR. Global landscapes of BnaNHXs will give an integrated understanding of their family evolution and molecular features, which will provide elite gene resources for the genetic improvement of plant SSR through regulating the NHX-mediated Na⁺ transport.

Water scarcity is considered to be a severe environmental constraint to plant survival and productivity. Studies on drought-tolerant plants would definitely promote a better understanding of the regulatory mechanism lying behind the adaptive response of plants to drought. Opisthopappus taihangensis (ling) shih is a typical drought-tolerant perennial plant species endemically distributed across the Taihang Mountains in China, but the underlying mechanism for drought tolerance of this particular species remains elusive. To mimic natural drought stress, O. taihangensis plants were treated with two different concentrations (25% and 5%) of polyethylene glycol (PEG6000), which represent the H group (high salinity) and the L group (low salinity), respectively. The physiological characteristics of these two groups of plants, including relative water content maintenance (RWC), proline content and chlorophyll content were assessed and compared with plants in the control group (CK), which had normal irrigation. There was not a significant difference in RWC when comparing plants in the L group with the control group. Proline was accumulated to a higher level, and chlorophyll content was decreased slightly in plants under low drought stress. In plants from the H group, a lower RWC was observed. Proline was accumulated to an even higher level when compared with plants from the L group, and chlorophyll content was further reduced in plants under high drought stress. Transcriptomic analysis was carried out to look for genes that are differentially expressed (DEGs) in O. taihangensis plants coping adaptively with the two levels of drought stress. A total of 23,056 genes are differentially expressed between CK and L, among which 12,180 genes are up-regulated and 10,876 genes are down-regulated. Between H and L, 6182 genes are up-regulated and 1850 genes are down-regulated, which gives a total of 8032 genes. The highest number of genes, that are differentially expressed, was obtained when a comparison was made between CK and H. A total of 43,074 genes were found to be differentially expressed with 26,977 genes up-regulated and 16,097 genes down-regulated. Further analysis of these genes suggests that many of the up-regulated genes are enriched in pathways involved in amino acid metabolism. Besides, 39 transcription factors (TFs) were found to be continuously up-regulated with the increase of drought stress level. Taken together, the results indicate that O. taihangensis plants are able to live adaptively under drought stress by responding physiologically and regulating the expression of a substantial number of drought-responsive genes and TFs to avoid adverse effects.

Background: Nitrogen (N), referred to as a “life element”, is a macronutrient essential for optimal plant growth and yield production. Amino acid (AA) permease (AAP) genes play pivotal roles in root import, long-distance translocation, remobilization of organic amide-N from source organs to sinks, and other environmental stress responses. However, few systematic analyses of AAPs have been reported in Brassica napus so far. Results: In this study, we identified a total of 34 full-length AAP genes representing eight subgroups (AAP1–8) from the allotetraploid rapeseed genome (A_nA_nC_nC_n, 2n = 4x = 38). Great differences in the homolog number among the BnaAAP subgroups might indicate their significant differential roles in the growth and development of rapeseed plants. The BnaAAPs were phylogenetically divided into three evolutionary clades, and the members in the same subgroups had similar physiochemical characteristics, gene/protein structures, and conserved AA transport motifs. Darwin’s evolutionary analysis suggested that BnaAAPs were subjected to strong purifying selection pressure. Cis-element analysis showed potential differential transcriptional regulation of AAPs between the model Arabidopsis and B. napus. Differential expression of BnaAAPs under nitrate limitation, ammonium excess, phosphate shortage, boron deficiency, cadmium toxicity, and salt stress conditions indicated their potential involvement in diverse nutrient stress responses. Conclusions: The genome-wide identification of BnaAAPs will provide a comprehensive insight into their family evolution and AAP-mediated AA transport under diverse abiotic stresses. The molecular characterization of core AAPs can provide elite gene resources and contribute to the genetic improvement of crop stress resistance through the modulation of AA transport.