Brassinosteroids (BRs) play an essential role in plant growth, development, and responses to diverse abiotic stresses. However, previous studies mainly analyzed how exogenous BRs influenced plant physiological reactions to drought stress, therefore, genetic evidences for the endogenous BRs-mediated regulation of plant responses still remain elusive. In this study, a key BRs biosynthetic gene, SoCYP85A1 was cloned from Spinacia oleracea, which has a complete open reading frame of 1,392 bp encoding a 464 amino acid peptide and shares high sequence similarities with CYP85A1 from other plants. The expression of SoCYP85A1 which was higher in leaf compared with root and stem, was induced by treatments of PEG6000, abscisic acid (ABA), low temperature and high salt. Increases in both SoCYP85A1 transcripts and endogenous BRs in transgenic tobacco which resulted in longer primary root and more lateral roots enhanced drought tolerance compared with wild types. The transgenic tobacco accumulated much lower levels of reactive oxygen species and malondialdehyde (MDA) than wild types did, accompanied by significantly higher content of proline and notably enhanced activities of antioxidant enzymes. Besides, transcriptional expressions of six stress-responsive genes were regulated to higher levels in transgenic lines under drought stress. Taken together, our results demonstrated that SoCYP85A1 involves in response to drought stress by promoting root development, scavenging ROS, and regulating expressions of stress-responsive genes.

Meloidogyne incognita is one of the most destructive agricultural pathogens around the world, resulting in severe damage to yield and quality in agricultural production. Biological control promises to be a great potential alternative to chemical agents against M. incognita. Paenibacillus polymyxa J2-4, isolated from ginger plants injured by M. incognita, has shown excellent biocontrol efficacy against M. incognita in cucumber. In vitro experiments with the strain J2-4 resulted in a correct mortality rate of 88.79% (24 h) and 98.57% (48 h) for second-stage juveniles (J2s) of M. incognita. Strain J2-4 significantly suppressed nematode infection on potted plants, with a 65.94% reduction in galls and a 51.64% reduction in eggs compared with the control. The split-root assay demonstrated that strain J2-4 not only reduced J2s’ invasion but also inhibited nematode development through the dependence on salicylic acid and jasmonic acid signaling of strain J2-4 induction of plant resistance in local and systemic roots of cucumbers. Genomic analysis of strain J2-4 indicated biosynthetic gene clusters encoding polymyxin, fusaricidin B, paenilan, and tridecaptin. In addition, genetic analysis showed that none of the genes encoding virulence factors were detected in the genome of J2-4 compared with the pathogenic Bacillus species. Taking all the data together, we conclude that P. polymyxa J2-4 has potential as a biological control agent against M. incognita on cucumbers and can be considered biologically safe when used in agriculture.

Maize (Zea mays) is one of the most important cereal crops worldwide. Insect control through host plant resistance plays an important part in improving both yield and quality of maize. Spodoptera exigua is a common insect pest causing destructive damages to maize. To comprehensively understand molecular mechanism of maize defense against S. exigua, integrated transcriptomics and metabolomics analyses were conducted in the insect-resistant maize inbred line CML139 infested with S. exigua for 24 h. 9845 differentially expressed genes and 34 significantly changed metabolites were identified in infested leaves. Maize transcriptional response to S. exigua infestation involved in genes encoding enzymes in biosynthetic process (ribosome, glycerolipid, glycerophospholipid metabolism), genes in valine, leucine and isoleucine degradation, phenylpropanoid pathway and transcription factors. By metabolism analysis, accumulations of amino acids, organic acids, phenylpropanoids and benzoxazinoids (Bxs) were significantly enhanced, with the exception of salicylic acid (SA) and jasmonic acid (JA). The integrated analysis of transcriptomic and metabolic data demonstrated that both transcripts and metabolites involved in phenylpropanoid and Bxs biosynthesis were differentially modulated in S. exigua infested leaves. This study is valuable in understanding the complex mechanism of interaction between plants and insect herbivores and provide a potential strategy to maize pest control.

Root-knot nematodes (RKNs) are highly specialized parasites that cause significant yield losses worldwide. In this study, we isolated Bacillus pumilus strain S1-10 from the rhizosphere soil of Zingiber officinale Rosc. plants and evaluated its fumigant activity against Meloidogyne incognita. S1-10 exhibited a strong repellent effect on second-stage juveniles (J2s) of M. incognita, and in vitro assays indicated that S1-10 volatile organic compounds (VOCs) suppressed J2 activity and egg hatching. Under greenhouse conditions, 71 and 79% reductions of nematodes and eggs were detected on plants treated with S-10 VOCs compared with controls. Ten VOCs were identified through gas chromatography and mass spectrometry (GC-MS), of which 2-(methylamino)-ethanol (2-ME) had strong fumigant activity against J2s of M. incognita, with an LC₅₀ value of 1.5 mM at 12 h. These results indicate that S1-10 represents a potential novel biocontrol agent for RKNs.

Black shank caused by Phytophthora nicotianae is one of the most devastating diseases in tobacco production. In this study, we characterized a novel cytochromic resistance gene, SoCYP85A1, from spinach, which was upregulated in response to P. nicotianae infection. Overexpression of SoCYP85A1 in tobacco resulted in remarkable resistance to pathogen inoculation, with diverse resistance levels in different transgenic lines. Meanwhile, a significant accumulation of castasterone (CS) was detected in transgenic plants when challenged with the pathogen. Moreover, activities of antioxidant enzymes were enhanced by SoCYP85A1 in the transgenic lines as compared to those in the wild types inoculated with P. nicotianae. In addition, the alteration of CS content resulted in interference of phytohormone homeostasis. Overall, these results demonstrate that SoCYP85A1 can participate in the defense response to P. nicotianae through the involvement of defense enzymes and by interaction with certain phytohormones. Our findings suggest that SoCYP85A1 could be used as a potential candidate gene for improving resistance to black shank disease in tobacco and other economic crops.