Biology subjects

Figon, F.

Publications and source records attributed to Figon, F..

3 recordsLinked to original sources

bioRxiv2021

Catabolism of lysosome-related organelles in color-changing spiders supports intracellular turnover of pigments

Pigment organelles of vertebrates belong to the lysosome-related organelle (LRO) family, of which melanin-producing melanosomes are the prototypes. While their anabolism has been extensively unraveled through the study of melanosomes in skin melanocytes, their catabolism remains poorly known. Here, we tap into the unique ability of crab spiders to reversibly change body coloration to examine the catabolism of their pigment organelles. By combining ultrastructural and metal analyses on high-pressure frozen integuments, we first assess whether pigment organelles of crab spiders belong to the LRO family and, second, how their catabolism is intracellularly processed. Using scanning-transmission electron microscopy, electron tomography and nanoscale Synchrotron-based scanning X-ray fluorescence, we show that pigment organelles possess ultrastructural and chemical hallmarks of LROs, including intraluminal vesicles and metal deposits, similar to melanosomes. Monitoring ultrastructural changes during bleaching suggests that the catabolism of pigment organelles involves the degradation and removal of their intraluminal content, possibly through lysosomal mechanisms. In contrast to skin melanosomes, anabolism and catabolism of pigments proceed within the same cell without requiring either cell death or secretion/phagocytosis. Our work hence provides support for the hypothesis that the endolysosomal system is fully functionalized for within-cell turnover of pigments, leading to functional maintenance under adverse conditions and phenotypic plasticity. First formulated for eye melanosomes in the context of human vision, the hypothesis of intracellular turnover of pigments gets unprecedented strong support from pigment organelles of spiders.

cell biology↗

bioRxiv2020

Ethylene is a local modulator of jasmonate-dependent phenolamide accumulation during Manduca sexta herbivory in Nicotiana attenuata

AO_SCPLOWBSTRACTC_SCPLOWRapid reconfigurations of intimately connected phytohormone signaling networks allow plants to tune their physiology to constantly varying ecological conditions. During insect herbivory, most of the induced changes in defense-related leaf specialized metabolites are controlled by jasmonate (JA) signaling, which, in the wild tobacco Nicotiana attenuata, recruits MYB8, a transcription factor controlling the accumulation of phenolic-polyamine conjugates (phenolamides). In this and other plant species, herbivory also locally triggers ethylene (ET) production but the outcome of the JA-ET crosstalk at the level of secondary metabolism regulation has remained superficially investigated. Here, we analyzed local and systemic herbivory-induced changes by mass spectrometry-based metabolomics in leaves of transgenic plants impaired in JA, ET and MYB8 signaling. Parsing deregulations in this factorial data-set identified a network of JA/MYB8-dependent phenolamides for which impairment of ET signaling attenuated their accumulation only in locally-damaged leaves. Further experiments revealed that ET, albeit biochemically interrelated to polyamine metabolism via the intermediate S-adenosylmethionine, does not impart on free polyamine levels, but instead significantly modulates phenolamide levels and marginally affected transcript levels in this pathway. This study identifies ET as a local modulator of phenolamide investments and provides a metabolomics data-platform to mine associations between herbivory-induced signaling and specialized metabolite groups in N. attenuata. SO_SCPLOWUMMARYC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWSTATEMENTC_SCPLOWHerbivory-elicited ethylene acts as a local enhancer of the production of jasmonate/MYB8-dependent phenolamides during the defense response of Nicotiana attenuata leaves against herbivory by the lepidopteran larva Manduca sexta.

plant biology↗

bioRxiv2019

Biological identification and localization of uncyclized xanthommatin, a key intermediate in ommochrome biosynthesis: an in vitro-in vivo study

Ommochromes are widespread pigments that mediate multiple functions in invertebrates. The two main families of ommochromes are ommatins and ommins, which both originate from the kynurenine pathway but differ in their backbone, thereby in their coloration and function. Despite its broad significance, how the structural diversity of ommochromes arises in vivo has remained an open question since their first description. In this study, we combined organic synthesis, analytical chemistry and organelle purification to address this issue. From a set of synthesized ommatins, we derived a fragmentation pattern that helped elucidating the structure of new ommochromes. We identified uncyclized xanthommatin as the elusive biological intermediate that links the kynurenine pathway to the ommatin pathway within ommochromasomes, the ommochrome-producing organelles. Due to its unique structure, we propose that uncyclized xanthommatin functions as a key branching metabolite in the biosynthesis and structural diversification of ommatins and ommins, from insects to cephalopods.

biochemistry↗