Larvae of Colorado potato beetle (Leptinotarsa decemlineata Say) resistant to double-stranded RNA (dsRNA) remain susceptible to small-molecule pesticides.

BACKGROUND: Implementation of resistance management tools is crucial for the continued efficacy of insect control technologies. An important aspect of insect resistance management (IRM) is the combined or sequential use of different modes-of-action to reduce selection pressure and delay evolution of resistance. This is especially important for insect pests with established ability to develop resistance to insecticides, such as the Colorado potato beetle (Leptinotarsa decemlineata, CPB). A new class of insecticides, based on double-stranded RNA (dsRNA) activating the gene silencing RNA-interference (RNAi) pathway, are currently under review for regulatory approval and commercial use in the USA against CPB. However, there is no information available on the potential for cross-resistance between RNAi insecticides and other classes of insecticides used against CPB. Herein, we aim to fill this knowledge gap by capitalizing on the availability of a CPB strain highly resistant to dsRNAs and test its susceptibility to diverse small-molecule insecticide classes compared to reference dsRNA-susceptible CPB strains. RESULTS: Differences in activity were observed among the four insecticides tested, with abamectin demonstrating highest activity against all three strains of CPB. However, no differences were observed among the dsRNA-resistant and susceptible CPB strains for any of the tested compounds. Overall, these results demonstrate lack of cross-resistance to commonly used chemical insecticides in the dsRNA-resistant strain of CPB. CONCLUSION: These data support the use of these different insecticide classes along with RNAi-based insecticides as part of an effective insect resistance management framework aimed at delaying resistance in CPB. © 2023 Society of Chemical Industry.

Selection for high levels of resistance to double-stranded RNA (dsRNA) in Colorado potato beetle (Leptinotarsa decemlineata Say) using non-transgenic foliar delivery.

Insecticidal double-stranded RNAs (dsRNAs) silence expression of vital genes by activating the RNA interference (RNAi) mechanism in insect cells. Despite high commercial interest in insecticidal dsRNA, information on resistance to dsRNA is scarce, particularly for dsRNA products with non-transgenic delivery (ex. foliar/topical application) nearing regulatory review. We report the development of the CEAS 300 population of Colorado potato beetle (Leptinotarsa decemlineata Say) (Coleoptera: Chrysomelidae) with > 11,100-fold resistance to a dsRNA targeting the V-ATPase subunit A gene after nine episodes of selection using non-transgenic delivery by foliar coating. Resistance was associated with lack of target gene down-regulation in CEAS 300 larvae and cross-resistance to another dsRNA target (COPI ß; Coatomer subunit beta). In contrast, CEAS 300 larvae showed very low (~ 4-fold) reduced susceptibility to the Cry3Aa insecticidal protein from Bacillus thuringiensis. Resistance to dsRNA in CEAS 300 is transmitted as an autosomal recessive trait and is polygenic. These data represent the first documented case of resistance in an insect pest with high pesticide resistance potential using dsRNA delivered through non-transgenic techniques. Information on the genetics of resistance and availability of dsRNA-resistant L. decemlineata guide the design of resistance management tools and allow research to identify resistance alleles and estimate resistance risks.

Activin A-derived human embryonic stem cells show increased competence to differentiate into primordial germ cell-like cells.

Protocols for specifying human primordial germ cell-like cells (hPGCLCs) from human embryonic stem cells (hESCs) remain hindered by differences between hESC lines, their derivation methods, and maintenance culture conditions. This poses significant challenges for establishing reproducible in vitro models of human gametogenesis. Here, we investigated the influence of activin A (ActA) during derivation and maintenance on the propensity of hESCs to differentiate into PGCLCs. We show that continuous ActA supplementation during hESC derivation (from blastocyst until the formation of the post-inner cell mass intermediate [PICMI]) and supplementation (from the first passage of the PICMI onwards) is beneficial to differentiate hESCs to PGCLCs subsequently. Moreover, comparing isogenic primed and naïve states prior to differentiation, we showed that conversion of hESCs to the 4i-state improves differentiation to (TNAP [tissue nonspecific alkaline phosphatase]+/PDPN [podoplanin]+) PGCLCs. Those PGCLCs expressed several germ cell markers, including TFAP2C (transcription factor AP-2 gamma), SOX17 (SRY-box transcription factor 17), and NANOS3 (nanos C2HC-type zinc finger 3), and markers associated with germ cell migration, CXCR4 (C-X-C motif chemokine receptor 4), LAMA4 (laminin subunit alpha 4), ITGA6 (integrin subunit alpha 6), and CDH4 (cadherin 4), suggesting that the large numbers of PGCLCs obtained may be suitable to differentiate further into more mature germ cells. Finally, hESCs derived in the presence of ActA showed higher competence to differentiate to hPGCLC, in particular if transiently converted to the 4i-state. Our work provides insights into the differences in differentiation propensity of hESCs and delivers an optimized protocol to support efficient human germ cell derivation.

Data on genetic potentiality of folk rice (Oryza sativa L.) genotypes from Koraput, India in reference to drought tolerance traits.

Precise physiological and molecular marker-based assessment provides information about the extent of genetic diversity, which helps for effective breeding programmes. We have conducted detailed physiological and molecular marker-based assessment of selected eight indigenous rice landraces from Koraput, India along with tolerant (N22) and susceptible (IR64) check varieties under control and simulated drought stress using polyethylene glycol (PEG) 6000. After exposure to different levels of drought stress, relative germination performance (RGP), seedling vigour index (SVI) and relative growth index (RGI) were significantly declined in all the rice landraces compared to the control plants and significant varietal differences were observed. Genetic relationship among the studied rice landraces was assessed with 24 previously reported drought tolerance linked Simple Sequence Repeat (SSR) markers. A total of 53 alleles were detected at the loci of the 24 markers across the 10 rice accessions. The Nei's gene diversity (He) and the polymorphism information content (PIC) ranged from 0 to 0.665 and 0 to 0.687, respectively. Six SSR loci, RM276, RM411, RM3, RM263, RM216 and RM28199, provided the highest PIC values and are potential for exploring the genetic diversity of studied rice lines for drought tolerance. Four rice genotypes (Butkichudi, Haldichudi, Machakanta and Kalajeera) showed the highest genetic distance with tolerant check variety (N22) and can be considered as valuable genetic resources for drought breeding program.