Defensive Role of Plant Latex on Insect Pests’ Suppression: A Critical Review

Over 350 million years have passed since the documentation of the first interaction between plants and insects. Numerous plant defense qualities and associated counter-adaptive features have developed as a result of these interactions between insects and plants. These characteristics might be either morphological or biological in nature. One of the most significant and useful biochemical characteristics in plants is latex. Latex has a sticky property due to presence of secondary metabolites in it, which aids in entangling or sealing the mouthparts of small insects. These metabolites also chemically interact with the insects interfering with crucial bodily processes. Plant latex has amazing properties that help protect plants from insects and inhibit them in general. It may be possible to control insect pests in a natural, secure, and long-lasting manner by correctly identifying plant latex with strong insecticidal properties and developing formulations of plant latex.

Functional characterization of(E)-β-caryophyllene synthase from lima bean and its up-regulation by spider mites and alamethicin

（E）-β-Caryophyllene is a sesquiterpene compound widely distributed in plants and functions in plant defence. However, little is known about the sequence and function of （E）-β-caryophyllene synthase in lima bean （Phaseolus lunatus）. Here, we report a new full-length cDNA （PICAHS） encoding （E）-β-caryophyllene synthase, a possible key enzyme of plant defence. The cDNA of PICAHS contains an open reading frame of 1 761 bp, encoding a protein of 586 amino acids with a predicted mass of 67.95 kDa. The deduced amino acid sequence shows 52% identity with sesquiterpene synthase MtCAHS of Med- icago truncatula. Based on phylogenetic analysis, PICAHS is classified as the terpene synthases （TPS）-a subfamily. The recombinant enzyme, expressed in Escherichia coil, catalysed the formation of a major product （E）-β-caryophyllene （82%） and a minor product a-humulene （18%） from farnesyl dJphosphate. Real-time quantitative PCR （qRT-PCR） analysis found that the PICAHS transcript was significantly up-regulated in leaves after treatment with spider mites and alamethicin （ALA）, suggesting its ecological function in plant defence.

A systematic review of the attractant-decoy and repellent- plant hypotheses: do plants with heterospecific neighbours escape herbivory?

Aims this systematic review highlights the relative support and implica-tions of the attractant-decoy and repellent-plant hypotheses,discuss-ing important linkages between these theories and the opportunity for novel integration into ecological and applied research.Methods an extensive systematic review of the current literature on the attract-ant-decoy and repellent-plant hypotheses was done to describe the following attributes of the research to date:(i)the geographic extent(country and biome)of studies on this topic,(ii)the scope of experi-mental designs used,(iii)the level of support for these hypotheses with respect to the breadth of ecological niches tested,(iv)the level of support for these hypotheses with respect to the classes of herbi-vores examined and,lastly,(v)the ecological impact or purpose of these studies.Herein,we summarize important research gaps in the empirical literature on this topic and identify novel opportunities for critical linkages between ecological and applied theories.Important Findingsa total of 37%of experiments testing these two associated hypotheses were done in North america,frequently in either temperate broadleaf(26%of studies)or taiga ecosystems(15%of studies).the majority of these studies involved experimental manipulations such as removing and transplanting vegetation and either tracked or excluded mammalian herbivores.Ecological implications were primarily examined(59%of studies),but there were also implications described for agriculture and commercial forestry in 22%of studies.the repellent-plant hypothesis was well supported in many ecological systems,particularly for mammalian herbivores,but the attractant-decoy hypothesis has been less frequently tested,thereby representing an important research gap.Insect herbivores were under-represented in all categories except in applied contexts such as commercial forestry and agriculture.there is a clear need for studies to connect these two ecological hypotheses with the management of agriculture and restoration efforts in many ecosystems.research on the co-evolution and facilitation between palatable and unpalatable plants also represents another novel area of future study.

Prickly pairs: the proportion of spinescent species does not differ between islands and mainlands

Aims Organisms on islands are thought to escape biotic pressure and lose defensive capabilities.However,broadscale,evidence-based tests of this idea are rare.In this study,we asked:(i)whether the proportion of spinescent plant species differed between islands and mainlands and(ii)whether the proportion of spinescent species increased with increasing island area and with decreasing island distance to mainland.Methods We compiled species lists for 18 island–mainland pairs around Australia.We classified 1129 plant species as spinescent or nonspinescent using published species descriptions.Important Findings There was no significant difference between the proportion of spinescent species found on islands and on mainlands.Proportions of spinescent species were not significantly related to island area or distance to mainland.Our results suggest that spinescence is just as important to island plants as it is to mainland plants,even for plants inhabiting small or distal islands.This is unexpected,given prevailing thought and previous work on island–mainland comparisons.Our study demonstrates the importance of testing well-accepted yet untested ideas.

comIntraspecific variation in heritable secondary metabolites and defensive strategies in a relict tree

Aims Key herbivory interaction traits such as plant defensive compounds may differ among populations of a single species due to the spatial variation in herbivore feeding guilds and the strength of the interac-tion.Moreover,the genealogy of population lineages could represent an additional source of variation interacting with the predominant eco-clinal trends.We tested for the existence of genetically based intraspecific variation in chemical defence profiles across the range of the relict tree Prunus lusitanica L.Additionally,we investigated geographical variation in defence inducibility and tested for the exist-ence of a trade-off between qualitative and quantitative defences.Methods We conducted a greenhouse experiment where 210 plants were grown under a common environment,comprising 10 different pop-ulations throughout the distribution range of the species and span-ning three separate regions:iberia,Morocco and Macaronesia.To test for the inducibility of defences,we artificially defoliated plants.Three treatments were established within each population:undam-aged,defoliated and sampled after 2 h,and defoliated and sampled after 72 h.The concentration of cyanogenic glycosides(prunasin)and phenolics was determined in leaf samples for all treatments.Important findings Basal levels of cyanogenics and phenolics significantly differed among populations and regions across the range of P.lusitanica,with this variation having a heritable basis.Cyanogenics(pruna-sin)were significantly higher in ancient Macaronesian populations,while phenolic concentrations were larger in iberia.The higher cyanogenic levels found in Macaronesia could be a consequence of the known stronger herbivory pressure in the islands than in iberia or the likely longer coevolutionary history with herbivores in this region.These findings indicate that the geographical variation of key ecological traits such plant chemical defences can be imprinted by phylogeographical signals,particularly in relict species.Regarding defence inducibility,prunasin increased after simulated herbivory whereas phenolics mostly decreased after defoliation.Variation in defence inducibility across populations and regions was evident,although no consistent patterns related to the variation in herbivore feeding guilds were observed,particularly among regions with and without ungulate browsing pressure.Finally,a trade-off among induced levels of qualitative(prunasin)and quantitative(phenolics)defences was detected in one of the defoliated treatments,likely as a result of a stronger resource limitation in damaged plants.