Tolerance enhancement of Dendrobium officinale by salicylic acid family-related metabolic pathways under unfavorable temperature.

BACKGROUND: Unfavorable temperatures significantly constrain the quality formation of Dendrobium officinale, severely limiting its food demand. Salicylic acid (SA) enhances the resistance of D. officinale to stress and possesses various analogs. The impact and mechanism of the SA family on improving the quality of D. officinale under adverse temperature conditions remains unclear. RESULTS: Combined with molecular docking analysis, chlorophyll fluorescence and metabolic analysis after treatments with SA analogues or extreme temperatures are performed in this study. The results demonstrate that both heat and cold treatments impede several main parameters of chlorophyll fluorescence of D. officinale, including the ΦPSII parameter, a sensitive growth indicator. However, this inhibition is mitigated by SA or its chemically similar compounds. Comprehensive branch imaging of ΦPSII values revealed position-dependent improvement of tolerance. Molecular docking analysis using a crystal structure model of NPR4 protein reveals that the therapeutic effects of SA analogs are determined by their binding energy and the contact of certain residues. Metabolome analysis identifies 17 compounds are considered participating in the temperature-related SA signaling pathway. Moreover, several natural SA analogs such as 2-hydroxycinnamic acid, benzamide, 2-(formylamino) benzoic acid and 3-o-methylgallic acid, are further found to have high binding ability to NPR4 protein and probably enhance the tolerance of D. officinale against unfavorable temperatures through flavone and guanosine monophosphate degradation pathways. CONCLUSIONS: These results reveal that the SA family with a high binding capability of NPR4 could improve the tolerance of D. officinale upon extreme temperature challenges. This study also highlights the collaborative role of SA-related natural compounds present in D. officinale in the mechanism of temperature resistance and offers a potential way to develop protective agents for the cultivation of D. officinale.

The reduced state of the plastoquinone pool is required for chloroplast-mediated stomatal closure in response to calcium stimulation.

Besides their participation in photosynthesis, leaf chloroplasts function in plant responses to stimuli, yet how they direct stimulus-induced stomatal movement remains elusive. Here, we showed that over-reduction of the plastoquinone (PQ) pool by dibromothymoquinone (DBMIB) was closely associated with stomatal closure in plants which required chloroplastic H2O2 generation in the mesophyll. External application of H2 O2 reduced the PQ pool, whereas the cell-permeable reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) reversed the DBMIB-induced over-reduction of the PQ pool and stomatal closure. Mesophyll chloroplasts are key players of extracellular Ca(2+) (Ca(2+)o)-induced stomatal closure, but when treated with either 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) or NAC they failed to facilitate Ca(2+)o-induced stomatal closure due to the inhibition of chloroplastic H2 O2 synthesis in mesophyll. Similarly, the Arabidopsis electron transfer chain-related mutants npq4-1, stn7 and cas-1 exhibited diverse responses to Ca(2+)o or DBMIB. Transcriptome analysis also demonstrated that the PQ pool signaling pathway shared common responsive genes with the H2 O2 signaling pathway. These results implicated a mechanism for chloroplast-mediated stomatal closure involving the generation of mesophyll chloroplastic H2O2 based on the reduced state of the PQ pool, which is calcium-sensing receptor (CAS) and LHCII phosphorylation dependent.

Molecular insights into the anti-spoilage effect of salicylic acid in Favorita potato processing.

Salicylic acid is a commonly used anti-spoilage agent to prevent browning and quality degradation during potato processing, yet its precise mechanism remains unclear. This study elucidates the role of StuPPO2, a functional protein in Favorita potato shreds, in relation to the anti-browning and starch degradation effects of 52 SA analogues. By employing molecular docking and Gaussian computing, SA localizes within the hydrophobic cavity of StuPPO2, facilitated by hydroxyl and carboxyl groups. The inhibitory effect depends on the distribution pattern of the maximal electrostatic surface potential, requiring hydroxyl ion potentials of >56 kcal/mol and carboxyl ion potentials of >42 kcal/mol, respectively. Multiomics analysis, corroborated by validation tests, indicates that SA synthetically suppresses activities linked to defense response, root regeneration, starch degradation, glycoalkaloids metabolism, and potato shred discoloration, thereby preserving quality. Furthermore, SA enhances antimicrobial and insect-repellent aromas, thereby countering biotic threats in potato shreds. These collective mechanisms underscore SA's anti-spoilage properties, offering theoretical foundations and potential new anti-browning agents for agricultural preservatives.

The genome of serotype VI Streptococcus agalactiae serotype VI and comparative analysis.

Streptococcus agalactiae (GBS) causes serious infections in humans and other species. A total of 25 complete GBS genomes, including the first sequenced serotype VI genome (GBS-M002), were compared in this study. The power law model suggested that the pan-genome of GBS is open, with approximately 1300 genes in the core genome of GBS, accounting for approximately 60% of the average genome content. GBS-M002 has 73 specific genes and is one of the five strains containing >60 specific genes. Based on COG (Cluster of Orthologous Groups of proteins) functional classification, 24% of the genes related to defense mechanisms are specific among the strains. A phylogenetic tree shows that GBS-M002 is closely related to certain strains of serotypes III and V from humans and to isolates of unknown serotype from dog and bovine hosts, suggesting the universal infection potential of GBS from humans to other mammal and fish hosts.

Transcriptome comparison reveals candidate genes responsible for the betalain-/anthocyanidin-production in bougainvilleas.

The occurrence of betalains and anthocyanins is mutually exclusive, which is a curious phenomenon in the plant kingdom, and the biochemical mechanisms for this restriction are unknown. In the present study, we performed transcriptome analysis of two betalain-producing species, red Bougainvillea glabra Choisy. 'Sanderiana' (R) and white B. glabra 'Alba' (W) by transcriptome sequencing. In total, we obtained 69692 (Red) and 60727 (White) genes with an average length of 665 and 728bp respectively. Out of 3106 significantly differentially-expressed genes (71%), 1003 were R-specific (32%), and 1605 were W-specific (52%). To validate betalain-/anthocyanidin-biosynthesis genes detected (cytochrome P 450 76AD1 (CYP76AD1), dihydroxy-phenylalanine (DOPA)-4,5-dioxygenase (DODA), cyclo DOPA-5-O-glycosyltransferase (cyclo-DOPA-5-GT) dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX)), real-time PCR was performed in leaves and three development stages of flowers in four Bougainvilleas, red R, white W, orange Bougainvillea×buttiana 'Salmoea' (O) and purple B. glabra 'Formosa' (P). Contents of betalains were also measured. The results showed that betalains accumulation was consistent with the expression level of DODA in O. A correlation between expression of CYP76AD1 and cyclo-DOPA-5GT and betalains was not discovered. This suggests that production of betacyanins was under the regulation of more complex factors. Both DFR and LDOX responsible for anthocyanidin production were first validated in floral organs and leaves in betalain-producing plants by real-time PCR. These findings suggest a fully functioning anthocyanin pathway, at least, to the stage of LDOX in bougainvilleas.

Hydrogen Sulfide-Mediated Polyamines and Sugar Changes Are Involved in Hydrogen Sulfide-Induced Drought Tolerance in Spinacia oleracea Seedlings.

Hydrogen sulfide (H2S) is a newly appreciated participant in physiological and biochemical regulation in plants. However, whether H2S is involved in the regulation of plant responses to drought stress remains unclear. Here, the role of H2S in the regulation of drought stress response in Spinacia oleracea seedlings is reported. First, drought stress dramatically decreased the relative water content (RWC) of leaves, photosynthesis, and the efficiency of PSII. Moreover, drought caused the accumulation of ROS and increased the MDA content. However, the application of NaHS counteracted the drought-induced changes in these parameters. Second, NaHS application increased the water and osmotic potential of leaves. Additionally, osmoprotectants such as proline and glycinebetaine (GB) content were altered by NaHS application under drought conditions, suggesting that osmoprotectant contributes to H2S-induced drought resistance. Third, the levels of soluble sugars and polyamines (PAs) were increased differentially by NaHS application in S. oleracea seedlings. Moreover, several genes related to PA and soluble sugar biosynthesis, as well as betaine aldehyde dehydrogenase (SoBADH), choline monooxygenase (SoCMO), and aquaporin (SoPIP1;2), were up-regulated by H2S under drought stress. These results suggest that H2S contributes to drought tolerance in S. oleracea through its effect on the biosynthesis of PAs and soluble sugars. Additionally, GB and trehalose also play key roles in enhancing S. oleracea drought resistance.

Hydrogen sulfide enhances salt tolerance through nitric oxide-mediated maintenance of ion homeostasis in barley seedling roots.

Hydrogen sulfide (H2S) and nitric oxide (NO) are emerging as messenger molecules involved in the modulation of plant physiological processes. Here, we investigated a signalling network involving H2S and NO in salt tolerance pathway of barley. NaHS, a donor of H2S, at a low concentration of either 50 or 100 µM, had significant rescue effects on the 150 mM NaCl-induced inhibition of plant growth and modulated the K(+)/Na(+) balance by decreasing the net K(+) efflux and increasing the gene expression of an inward-rectifying potassium channel (HvAKT1) and a high-affinity K(+) uptake system (HvHAK4). H2S and NO maintained the lower Na(+) content in the cytoplast by increasing the amount of PM H(+)-ATPase, the transcriptional levels of PM H(+)-ATPase (HvHA1) and Na(+)/H(+) antiporter (HvSOS1). H2S and NO modulated Na(+) compartmentation into the vacuoles with up-regulation of the transcriptional levels of vacuolar Na(+)/H(+) antiporter (HvVNHX2) and H(+)-ATPase subunit ß (HvVHA-ß) and increased in the protein expression of vacuolar Na(+)/H(+) antiporter (NHE1). H2S mimicked the effect of sodium nitroprusside (SNP) by increasing NO production, whereas the function was quenched with the addition of NO scavenger. These results indicated that H2S increased salt tolerance by maintaining ion homeostasis, which were mediated by the NO signal.