Biology subjects

Chalivendra, S.

Publications and source records attributed to Chalivendra, S..

3 recordsLinked to original sources

bioRxiv2023

Selected humanization of yeast U1 snRNP leads to global suppression of pre-mRNA splicing and mitochondrial dysfunction in the budding yeast

The recognition of 5 splice site (5 ss) is one of the earliest steps of pre-mRNA splicing. To better understand the mechanism and regulation of 5 ss recognition, we selectively humanized components of the yeast U1 snRNP to reveal the function of these components in 5 ss recognition and splicing. We targeted U1C and Luc7, two proteins that interact with and stabilize the yeast U1 (yU1) snRNA and the 5 ss RNA duplex. We replaced the Zinc-Finger (ZnF) domain of yU1C with its human counterpart, which resulted in cold-sensitive growth phenotype and moderate splicing defects. Next, we added an auxin-inducible degron to yLuc7 protein and found that Luc7-depleted yU1 snRNP resulted in the concomitant loss of PRP40 and Snu71 (two other essential yeast U1 snRNP proteins), and further biochemical analyses suggest a model of how these three proteins interact with each other in the U1 snRNP. The loss of these proteins resulted in a significant growth retardation accompanied by a global suppression of pre-mRNA splicing. The splicing suppression led to mitochondrial dysfunction as revealed by a release of Fe2+ into the growth medium and an induction of mitochondrial reactive oxygen species. Together, these observations indicate that the human U1C ZnF can substitute that of yeast, Luc7 is essential for the incorporation of the Luc7-Prp40-Snu71 trimer into yeast U1 snRNP, and splicing plays a major role in the regulation of mitochondria function in yeast.

biochemistry↗

bioRxiv2020

A tale of two transcriptomic responses in agricultural pests via host defenses and viral replication

BackgroundAutographa californica Multiple Nucleopolyhedrovirus (AcMNPV) is a baculovirus with a high potential for its use as a biopesticide against arthropod pests. The budded form of the virus causes a systemic infection when it escapes the midgut to enter the hemolymph of susceptible hosts. Yet, the specific molecular processes underlying the biocidal activity of AcMNPV on its insect hosts are largely unknown. ResultsIn this study, we describe the transcriptional responses in two major pests, Spodoptera frugiperda and Trichoplusia ni, to determine the host-pathogen responses during AcMNPV infection, concurrently with the viral response to the host. We assembled species-specific de novo reference transcriptomes of the hemolymph to identify key transcripts that respond during pathogenesis in these arthropod models where genomic resources are sparse. We found that the suppression of transcriptional processes related to chitin, a metabolite critical for basement membrane stability and tracheal development are central in establishing a systemic infection. Synergistic transcriptional support was observed to suggest suppression of immune responses and induction of oxidative stress indicating disease progression in the host. The entire AcMNPV core genome was expressed in the host hemolymph and viral genes predominantly associated with the budded virus replication, structure, and movement were more abundant than those associated with the occlusion-derived virus. Genes known to directly arrest host cell cycle and development were among the most abundant AcMNPV transcripts in infected hosts. Interestingly, several of the host genes (e.g. Chitin synthase) that were targeted by the pathogen as revealed by our study are also targets of several chemical insecticides currently used commercially to control arthropod pests. ConclusionsOur results reveal an extensive overlap between biological processes represented by genes differently expressed in both hosts, as well as convergence on highly abundant viral genes expressed in the two hosts, providing an overview of the host-pathogen transcriptomic landscape during systemic infection. Given the diversity of AcMNPV strains that infect a wide range of insect hosts, our study provides a framework where pathogen strains could be selected to target specific host genes that facilitates modulation of the infection strength and specificity of the susceptible hosts.

genomics↗

bioRxiv2020

Low aflatoxin levels and flowering delay in Aspergillus flavus-resistant maize lines are correlated with increased corn earworm damage and enhanced seed fumonisin content

Preharvest mycotoxin contamination of field-grown crops is influenced not only by the host genotype, but also inoculum load, insect pressure and their confounding interactions with seasonal weather. In two field trials, we observed a preferred natural infestation of specific maize (Zea mays L.) genotypes by corn earworm (Helicoverpa zea Boddie) and investigated this unexpected interaction. These studies involved four maize lines with contrasting levels of resistance to Aspergillus flavus. The resistant lines had 7 to 14-fold greater infested ears than the susceptible lines. However, seed aflatoxin B1 levels, in mock- or A. flavus-inoculated ears were consistent with maize genotype resistance to A. flavus. Further, the corn earworm-infested ears had greater levels of fumonisin content in seeds than uninfested ears, indicating that the insect may have vectored native Fusarium verticillioides inoculum. The two maize lines with heavy infestation showed delayed flowering. The availability of young silk for egg-laying could have been a factor in the pervasive corn earworm damage of these lines. At the same time, H. zea larvae reared on AF-infused diet showed decreasing mass with increasing AF and >30% lethality at 250 ppb. In contrast, corn earworm was tolerant to fumonisin with no significant loss in mass even at 100 ppm, implicating the low seed aflatoxin content as a predominant factor for the prevalence of corn earworm infestation and the associated fumonisin contamination in A. flavus resistant lines. These results highlight the need for integrated strategies targeting mycotoxigenic fungi and their insect vectors to enhance the safety of crop commodities. IMPORTANCEAspergillus and Fusarium spp. not only cause ear rots in maize leading to crop loss, they can also contaminate the grain with carcinogenic mycotoxins. Incorporation of genetic resistance into breeding lines is an ideal solution for mycotoxin mitigation. However, the goal is fraught by a major problem. Resistance for AF or FUM accumulation is quantitative and contributed by several loci with small effects. Our work reveals that host phenology (flowering time) and insect vector-mycotoxin interactions can further confound breeding efforts. A host genotype even with demonstrable resistance can become vulnerable due to seasonal variation in flowering time or an outbreak of chewing insects. Incorporation of resistance to a single mycotoxin accumulation and not pairing it with insect resistance may not adequately ensure food safety. Diverse strategies including host-induced silencing of genes essential for fungal and insect pest colonization and broad-spectrum biocontrol systems need to be considered for robust mycotoxin mitigation.

plant biology↗