A simplified protocol to obtain transgenic tomato plants was established. The effects of culture media composition and Agrobacterium concentration were evaluated. The highest shoot-forming capacity index (5.6) was observed when leaf explants were cultured for 6 weeks with 2 mg·L ⁻¹ zeatin, 0.1 mg·L ⁻¹ indoleacetic acid, and 300 mg·L ⁻¹ timentin. Shoot elongation and root formation were performed in one step on growth regulator-free media. The highest percentage (82%) of fully developed plantlets was obtained when shoots were cultured for 4 weeks with 0.5× Murashige and Skoog (MS) media and 15 g·L ⁻¹ sucrose. A 100% of plant survival rate was observed after 4 weeks of being transplanted to ex vitro conditions followed by fruit production (15 fruits/plant) after 2 more weeks. Transient expression of β-glucuronidase was visualized in 100% of the leaf explants infected with Agrobacterium at an OD ₆₀₀ = 0.5 and cocultured for 48 h with 2 mg·L ⁻¹ benzylaminopurine, 0.1 mg·L ⁻¹ naphthaleneacetic acid, and 100 μM acetosyringone. Stable transformation was confirmed by histochemical glucuronidase assay and polymerase chain reaction (PCR) analysis with a total efficiency of 19.1%. The complete protocol, from shoot induction to fruit production of soil-adapted transgenic plants can be accomplished in only 4 months, and it seems to be very useful for both micropropagation and genetic transformation purposes.

Fusarium verticillioides (Fv) is a mycotoxin-producing phytopathogen causing ear and root rot in maize. Bacillus cereus strain B25 is a maize endophyte and an effective biological control agent against Fv. The B25 genome contains several genes associated with fungal antagonism, including lytic enzymes (chitinases A and B, chitosanase and glycoside hydrolase), siderophores (petrobactin and bacillibactin), antibiotics (surfactin), and biofilm. This study aimed to elucidate which B25 antagonistic mechanisms are implicated in Fv biocontrol. The expression of twelve B25 genes was evaluated by qRT-PCR after 3–30 h of confrontation between B25 and Fv. All B25 genes tested were induced, mainly between 6 and 24 h, while none was induced at 3 h. Lytic enzyme genes were induced at different times, with three of them occurring at 12 h. Chitinase and chitosanase activities were induced after 6 and 12 h, respectively, and gradually increased until 30 h. Biofilm formation was detected only when B25 interacted with Fv. Images of the B25-Fv interaction and measurements at 24 and 30 h showed little branching or abnormal mycelial growth, suggesting cell wall damage. In conclusion, when B25 is confronted against Fv, all B25 antagonistic mechanisms tested appear to be involved in Fv growth control.

Huanglongbing (HLB) is one of the most destructive diseases threatening citriculture worldwide. This disease has been associated with α-proteobacteria species, namely Candidatus Liberibacter. Due to the unculturable nature of the causal agent, it has been difficult to mitigate the disease, and nowadays a cure is not available. MicroRNAs (miRNAs) are key regulators of gene expression, playing an essential role in abiotic and biotic stress in plants including antibacterial responses. However, knowledge derived from non-model systems including Candidatus Liberibacter asiaticus (CLas)-citrus pathosystem remains largely unknown. In this study, small RNA profiles from Mexican lime (Citrus aurantifolia) plants infected with CLas at asymptomatic and symptomatic stages were generated by sRNA-Seq, and miRNAs were obtained with ShortStack software. A total of 46 miRNAs, including 29 known miRNAs and 17 novel miRNAs, were identified in Mexican lime. Among them, six miRNAs were deregulated in the asymptomatic stage, highlighting the up regulation of two new miRNAs. Meanwhile, eight miRNAs were differentially expressed in the symptomatic stage of the disease. The target genes of miRNAs were related to protein modification, transcription factors, and enzyme-coding genes. Our results provide new insights into miRNA-mediated regulation in C. aurantifolia in response to CLas infection. This information will be useful to understand molecular mechanisms behind the defense and pathogenesis of HLB.