Emerging role of roots in plant responses to aboveground insect herbivory

Plants have evolved complex biochemical mechanisms to counter threats from insect herbivory. Recent research has revealed an important role of roots in plant responses to above ground herbivory （AGH）. The involvement of roots is integral to plant resistance and tolerance mechanisms. Roots not only play an active role in plant defenses by acting as sites for biosynthesis of various toxins and but also contribute to tolerance by storing photoassimilates to enable future regrowth. The interaction of roots with beneficial soil- borne microorganisms also influences the outcome of the interaction between plant and insect herbivores. Shoot-to-root communication signals are critical for plant response to AGH. A better understanding of the role of roots in plant response to AGH is essential in order to develop a comprehensive picture of plant-insect interactions. Here, we summarize the current status of research on the role of roots in plant response to AGH and also discuss possible signals involved in shoot-to-root communication.

The evolutionary strategies of plant defenses have a dynamic impact on the adaptations and interactions of vectors and pathogens

Plants have evolved and diversified to reduce the damages imposed by in- fectious pathogens and herbivorous insects. Living in a sedentary lifestyle, plants are constantly adapting to their environment. They employ various strategies to increase per- formance and fitness. Thus, plants developed cost-effective strategies to defend against specific insects and pathogens. Plant defense, however, imposes selective pressure on in- sects and pathogens. This selective pressure provides incentives for pathogens and insects to diversify and develop strategies to counter plant defense. This results in an evolution- ary arms race among plants, pathogens and insects. The ever-changing adaptations and physiological alterations among these organisms make studying plant-vector-pathogen interactions a challenging and fascinating field. Studying plant defense and plant protec- tion requires knowledge of the relationship among organisms and the adaptive strategies each organism utilize. Therefore, this review focuses on the integral parts of plant-vector- pathogen interactions in order to understand the factors that affect plant defense and disease development. The review addresses plant-vector-pathogen co-evolution, plant defense strategies, specificity of plant defenses and plant-vector pathogen interactions. Improving the comprehension of these factors will provide a multi-dimensional perspective for the future research in pest and disease management.

Diurnal feeding as a potential mechanism of osmoregulation in aphids

Diurnal variation in phloem sap composition has a strong infuence on aphid performance.The sugar-rich phloem sap serves as the sole diet for aphids and a suite of physiological mechanisms and behaviors allowv them to tolerate the high osmotic stress.Here,we tested the hypothesis that night-time feeding by aphids is a behavior that takes advantage of the low sugar diet in the night to compensate for osmotic stress incurred while feeding on high sugar diet during the day.Using the electrical penetration graph(EPG)technique.we examined the eiects of diurmal rhythm on feeding behaviors of bird cherry-oat aphid(Rhopalosiphurm padi L.)on wheat.A strong diurmal rhythm in aphids as indicated by the presence of a cyclical pattern of expression in a core clock gene did not impact aphid feeding and similar feeding behaviors were observed during day and night.The major difference observed between day and night feeding was that aphids spent significantly longer time in phloem salivation during the night compared to the day.In contrast,aphid hydration was reduced at the end of the day-time feeding compared to end of the night-time fepding.Gene expression analysis of R.padi osmoregulatory genes indicated that sugar break down and water transport into the aphid gut was reduced at night.These data suggest that while diumal variation occurs in phloem sap composition,aphids use night time feeding to overcome the high osmotic stress incurred while feeding on sugar-rich phloem sap during the day.

High-throughput molecular gut content analysis of aphids identifies plants relevant for potato virus Y epidemioiogy

Aphids are phloem-feeding insects that reduce crop productivity due to feeding and transmission of plant viruses.When aphids disperse across the landscape to colonize new host plants,they will often probe on a wide variety of nonhost plants before settling on a host suitable for feeding and reproduction.There is limited understanding of the diversity of plants that aphids probe on within a landscape,and characterizing this diversity can help us better understand host use patterns of aphids.Here,we used gut content analysis(GCA)to identify plant genera that were probed by aphid vectors of potato virus Y(PVY).Aphids were trapped weekly near potato fields during the growing seasons of 2020 and 2021 in San Luis Valley in Colorado.High-throughput sequencing of plant barcoding genes,trnF and ITS2,from 200 individual alate(i.e.,winged)aphids representing nine vector species of PVY was performed using the PacBio sequencing platform,and sequences were identi-fied to genus using NCBI BLASTn.We found that 34.7%of aphids probed upon presumed PVY host plants and that two of the most frequently detected plant genera,Solanum and Brassica,represent important crops and weeds within the study region.We found that 75%of aphids frequently probed upon PVY nonhosts including many species that are outside of their reported host ranges.Additionally,19%of aphids probed upon more than one plant species.This study provides the first evidence from high-throughput molecular GCA of aphids and reveals host use patterns that are relevant for PVY epidemiology.