Biology subjects

Malka, O.

Publications and source records attributed to Malka, O..

3 recordsLinked to original sources

bioRxiv2026

An Integrative Taste Receptor Links pH and Amino Acids to Sugar Sensing in Bemisia tabaci

Phloem-feeding insects execute complex behavioral decisions to secure essential nutrients from a diet characterized by nitrogen scarcity and severe osmotic pressure due to high sucrose concentrations. We investigated the sensory mechanisms underlying these decisions in the phloem-feeding whitefly Bemisia tabaci. We demonstrate that the sweet taste receptor BtabGR1, expressed in mouthpart and gut tissues, integrates three environmental chemical cues: sucrose concentration, the presence of the essential amino acid arginine, and pH values. Arginine is a pH-dependent positive modulator of sucrose sensing, increasing receptor responses nearly fourfold under apoplast-like conditions and more than doubling the receptor responses in the gut luminal environment. Insects show a strong feeding preference for arginine-containing diets in dual-choice bioassays, with markedly higher intake when arginine is present. RNAi-mediated silencing of BtabGR1 disrupt intake regulation, leading to increased honeydew excretion. These findings suggest a putative link between arginine and the BtabGR1 receptor in regulating both feeding-site evaluation and diet ingestion. Furthermore, the ability to integrate three distinct environmental cues makes BtabGR1 one of the most complex interdependent sensory systems described for a single insect chemoreceptor.

physiology↗

bioRxiv2026

Creating resistance to the whitefly Bemisia tabaci in cassava through RNAi-mediated targeting of multiple insect metabolic processes

It is commonplace in East Africa for 100% of cassava fields to be infected with Cassava mosaic disease (CMD) and/or Cassava brown streak disease (CBSD), resulting in annual losses of more than US$1.25 billion and reduced food and economic security for farming households. The vector of both diseases is the African cassava species of the whitefly Bemisia tabaci. Since the late 1990s, there has been an unprecedented increase in whitefly populations, to the extent that they are referred to as "super-abundant". Research efforts since the late 1990s has focused mainly on developing plant resistance to the viral pathogens and paid scant attention to understanding the root causes of disease epidemics or the control of whitefly infestation. Here, we aimed at developing long-term whitefly-control solutions using an in-planta RNA interference (RNAi) approach. First, transcriptome analysis identified candidate genes that play key roles in whitefly biology: osmoregulation, sugar metabolism and transport, symbiosis with endosymbiotic bacteria and detoxification of phytotoxins. Then, fifteen RNAi inverted repeat constructs were produced, designed to target the candidate genes and 140 independent transgenic lines were generated in cassava variety NASE 13. Whole plant bioassays showed insecticidal activity of transgenic plants, reaching 58% lethality for adults within 7 days and 75-90% lethality of nymphs after 25 days, compared to control plants. Target genes were confirmed to be downregulated by up to 2.5-fold in adult whiteflies and nymphs. We used population dynamics modelling to predict the potential of the RNAi technology to control whiteflies under field conditions in East Africa.

bioengineering↗

bioRxiv2018

A transmissible RNA pathway in honey bees

One of the characteristics of RNA interference (RNAi) is systemic spread of the silencing signal among cells and tissues throughout the organism. Systemic RNAi, initiated by double-stranded RNA (dsRNA) ingestion, has been reported in diverse invertebrates, including honey bees, demonstrating environmental RNA uptake that undermines homologous gene expression. However, the question why any organism would take up RNA from the environment has remained largely unanswered. Here, we report on horizontal RNA flow among honey bees mediated by secretion and ingestion of worker and royal jelly diets. We show that ingested dsRNA spreads through the bees hemolymph associated with a protein complex. The systemic dsRNA is secreted with the jelly and delivered to larvae via ingestion. Furthermore, we demonstrate that transmission of jelly-secreted dsRNA to larvae is biologically active and triggers gene knockdown that lasts into adulthood. Finally, RNA extracted from worker and royal jellies harbor differential naturally occurring RNA populations. Some of these RNAs corresponded to honey bee protein coding genes, transposable elements, non-coding RNA and exogenous viruses. These results reveal an inherent property of honey bees to share RNA among individuals and generations. Thus, our findings suggest a transmissible RNA pathway, playing a role in social immunity and epigenetic dynamics among honey bees and potentially other closely interacting organisms.\n\nSIGNIFICANCEHoney bees are eusocial insects, living in a colony that is often described as a superorganism. RNA mobility among cells of an organism has been documented in plants and animals. Here we show that RNA spreads further in honey bees, and is horizontally transferred between individuals and across generations. We found that honey bees share biologically active RNA through secretion and ingestion of worker and royal jellies. Such RNA initiated RNA interference, which is a known defense mechanism against viral infection. Furthermore, we characterized diverse RNA profiles of worker and royal jelly, including fragmented viral RNA. Our findings demonstrate a transmissible RNA pathway with potential roles in social immunity and epigenetic signaling among members of the hive.

molecular biology↗