María del Pilar Plastine

This study characterizes the cytogenetic diversity of maize landraces from Northern Argentina, a region comprising Northwestern Argentina (NWA) and Northeastern Argentina (NEA). New data from four NWA landraces were analyzed using DAPI banding, fluorescence in situ hybridization, and flow cytometry. Intra- and inter-populational variation was detected in heterochromatin content (2.06%–12.6%), as well as in the number (3–15), size, and chromosomal position of knobs. Genome size (2C value) ranged from 5.27 to 5.74 pg, and numerical polymorphism (0–2) of B chromosomes was observed. Consensus idiograms were constructed for each studied landrace. A quantitative analysis combining these data with previously published information on Argentine maize revealed a negative association between knob heterochromatin content and cultivation altitude. In NWA landraces, genome size was also negatively associated with altitude, whereas no such relationship was detected when NWA and NEA data were analyzed together. In NEA landraces, which grow within a narrow altitudinal range, genome size variability may be influenced by local farmers selection practices, whereas in NWA landraces cytogenetic variation may reflect multifactorial anthropogenic and environmental influences. B chromosomes were recorded exclusively at altitudes above 2000 m.a.s.l. The observed cytogenetic patterns are discussed in the context of ecogeographic differentiation among maize landraces.

Summary: Baculoviruses are insect-specific viruses primarily employed in biological pest control and recombinant protein expression. As biopesticides, they offer numerous advantages over chemical pesticides and hold significant potential for application in integrated pest management (IPM). However, their slower action compared to conventional synthetic strategies has limited their widespread adoption. This study aimed to investigate the impact of incorporating a viral protein, AcChiA chitinase, which disrupts the gut peritrophic membrane of susceptible insects, into AcMNPV occlusion bodies in trans . This was achieved through the development of an insect cell line that facilitates the passive incorporation of this protein. The presence of ChiA was detected in dissolved occlusion bodies (OBs) preparations from infected transgenic lines, in a method-dependent manner, with the stronger signals observed in chimeric polyhedra. It is hypothesized that ChiA in OBs will increase peritrophic membrane permeability and facilitate primary infection. In bioassays, OBs produced in ChiA-expressing lines were associated with higher larval mortality than OBs produced in Sf9, consistent with a ChiA-mediated effect. Notably, the addition of ChiA proteins from stably transformed insect cell lines improved infection rates, particularly in recombinant baculoviruses, which exhibited a significant reduction in occlusion-derived virion (ODV) occlusion. This underscores the critical role of these proteins in the oral infection process. Consequently, it was possible to incorporate the ChiA protein from stably transformed insect cell lines into wild-type and recombinant baculovirus occlusion bodies, paving the way for potential applications in IPM with AcMNPV.

Background/Objectives: Baculoviruses represent promising gene delivery vectors for mammalian systems, combining high safety profiles with substantial cargo capacity. While pseudotyping with vesicular stomatitis virus G-protein (VSV-G) enhances transduction efficiency, optimal expression strategies during the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infection cycle remain unexplored. This study investigates how VSV-G expression timing affects pseudotype incorporation into budded virions (BVs) and subsequent transduction efficacy. Methods: Three recombinant AcMNPV constructs were generated, each expressing VSV-G under distinct baculoviral promoters (ie1, gp64, and p10) and GFP via a CMV promoter. VSV-G incorporation was verified by Western blot, while transduction efficiency was quantified in mammalian cell lines (fluorescence microscopy/flow cytometry) and rat hind limbs. Viral productivity was assessed through production kinetics and plaque assays. Results: All the pseudotyped viruses showed significantly enhanced transduction capacity versus controls, strongly correlating with VSV-G incorporation levels. The p10 promoter drove the highest VSV-G expression and transduction efficiency. Crucially, BV production yields and infectivity remained unaffected by VSV-G expression timing. The in vivo results mirrored the cell culture findings, with p10-driven constructs showing greater GFP expression at low doses (10⁴ virions). Conclusions: Strategic VSV-G expression via very late promoters (particularly p10) maximizes baculoviral transduction without compromising production yields. This study establishes a framework for optimizing pseudotyped BV systems, demonstrating that late-phase glycoprotein expression balances high mammalian transduction with preserved insect-cell productivity—a critical advancement for vaccine vector development.