| The mealworm Tenebrio molitor. (A) Life cycle showing larva, pupa and adult. Epic mealworms: Weebly page by students M. Downey, L. McFarland, and D. Bergeron, STU bachelor of Education 2014 (EDUC 5473). From Google images (no conditions for copyright published, apparently freely available). (B) Picture by Amazon of mealworm larvae as they are commercially marketed mainly for pet food. Open access.
Farnesol, the sesquiterpenoid precursor of the six presently known insect juvenile hormones (JHs) was for the first time chemically identified in 1961, not in JH synthesizing glands or whole body extracts, but in excrements of the mealworm Tenebrio molitor. This finding was thought to be irrelevant and remained unexplored. In 1970, it was reported...
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... soon became clear that the active substance might belong to the isoprenoids. It was Schmialek (7) who chemically identified the first JH-active substances, namely the isoprenoids farnesol and farnesal, in the common mealworm Tenebrio (Figure 2). These isoprenoid were not isolated and identified from whole body extracts nor from particular glands, but from extracts of Tenebrio excrements. ...
... It acts as a precursor of the juvenile hormones of holometabolous insects and its absence in the larval stage induces metamorphosis. 52 Knowing the MoA of farnesol would allow for an improved effectiveness in the formulations, because if its activity is the result of a hormonal effect, its application should be performed during the nymphal stages of aphids. This could explain why it is more effective when applied to smaller colonies (with a greater number of nymphs). ...
Background: Myzus persicae (Hemiptera: Aphididae) is considered one of most important agricultural pests in the world. It is one of the main pests in protected pepper crops under greenhouse conditions in Southeastern Spain, but its control is limited due to few available authorized insecticides and their incompatibility with the natural enemies. Some essential oils and pure compounds such as anise (Pimpinella anisum) or farnesol are repellent and/or toxic to aphids. Their use as a botanical insecticides can be an alternative for aphid control in pepper. Results: The effect of farnesol was evaluated against Myzus persicae in a new bioassay developed to test the contact effect (aqueous formulation of the products) on aphids in laboratory conditions. Aniseed essential oil, geraniol, and (Z)-jasmone at 0.6% causes an aphid mortality of over 50%; and farnesol was the most effective (93.67% of mortality). Farnesol nanoemulsions between 0.2-0.6% were formulated with an IKA-Labor Pilot dispersing machine (7940 rev/min for ten minutes) using Tween 80 as a surfactant. These formulations were tested on field experiments (greenhouse conditions) on pepper crops for two years. Foliar applications of farnesol at a concentration of 0.4% on field conditions causes a high reduction in aphid populations, with efficacies between ≈70-80% with respect to the control, similar to the efficacy of the reference pyrethrins insecticide or even higher. Conclusion: Farnesol showed a great aphicidal effect against Myzus persicae. The use of this molecule in integrated pest management programs combined with natural enemies is a good option in the future. This article is protected by copyright. All rights reserved.
Integrative Physiology, a section of the journal Frontiers in Physiology The extensive literature dealing with the Golgi system emphasizes its role in protein secretion and modification, usually without specifying from which evolutionary ancient cell physiological necessity such secretion originated. Neither does it specify which functional requirements the secreted proteins must meet. From a reinterpretation of some classical and recent data gained mainly, but not exclusively, from (insect) endocrinology, the view emerged that the likely primordial function of the rough endoplasmic reticulum (RER)-Golgi complex in all eukaryotes was not the secretion of any type of protein but the removal of toxic excess Ca 2+ from the cytoplasm. Such activity requires the concurrent secretion of large amounts of Ca 2+-carrying/transporting proteins acting as a micro-conveyor belt system inside the RER-Golgi. Thus, (fitness increasing) protein secretion is subordinate to Ca 2+ removal. Milk with its high content of protein and Ca 2+ (60-90 mM vs. 100 nM in unstimulated mammary gland cells) is an extreme example. The sarco(endo)plasmatic reticulum Ca 2+-ATPases (SERCAs) and SPCA1a Ca 2+ /Mn 2+ transport ATPases are major players in Ca 2+ removal through the Golgi. Both are blocked by the sesquiterpenoid thapsigargin. This strengthens the hypothesis (2014) that endogenous farnesol-like sesquiterpenoids (FLSs) may act as the long sought for but still unidentified agonist(s) for Ca 2+-pumps in both the ER and Golgi. A second putative function also emerges. The fusion of both the incoming and outgoing transport vesicles, respectively, at the cis-and trans-side of Golgi stacks, with the membrane system requiring high flexibility and fast self-closing of the involved membranes. These properties may-possibly partially-be controlled by endogenous hydrophobic membrane "fluidizers" for which FLSs are prime candidates. A recent reexamination of unexplained classical data suggests that they are likely synthesized by the Golgi itself. This game-changing hypothesis is endorsed by several arguments and data, some of which date from 1964, that the insect corpus allatum (CA), which is the major production site of farnesol-esters, has active Golgi systems. Thus, in addition to Frontiers in Physiology | www.frontiersin.org 1 October 2020 | Volume 11 | Article 542879 De Loof and Schoofs Undervalued Functions of Golgi Apparatus secreting FLS, in particular juvenile hormone(s), it also secretes a protein(s) or peptide(s) with thus far unknown function. This paper suggests answers to various open questions in cell physiology and general endocrinology.