AA15 lytic polysaccharide monooxygenase is required for efficient chitinous cuticle turnover during insect molting

Abstract

Microbial lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of crystalline polysaccharides including chitin and cellulose. The discovery of a large assortment of LPMO-like proteins widely distributed in insect genomes suggests that they could be involved in assisting chitin degradation in the exoskeleton, tracheae and peritrophic matrix during development. However, the physiological functions of insect LPMO-like proteins are still undetermined. To investigate the functions of insect LPMO15 subgroup I-like proteins (LPMO15-1s), two evolutionarily distant species, Tribolium castaneum and Locusta migratoria, were chosen. Depletion by RNAi of T. castaneum TcLPMO15-1 caused molting arrest at all developmental stages, whereas depletion of the L. migratoria LmLPMO15-1, prevented only adult eclosion. In both species, LPMO15-1-deficient animals were unable to shed their exuviae and died. TEM analysis revealed failure of turnover of the chitinous cuticle, which is critical for completion of molting. Purified recombinant LPMO15-1-like protein from Ostrinia furnacalis (rOfLPMO15-1) exhibited oxidative cleavage activity and substrate preference for chitin. These results reveal the physiological importance of catalytically active LPMO15-1-like proteins from distant insect species and provide new insight into the enzymatic mechanism of cuticular chitin turnover during molting.

Reductants fuel lytic polysaccharide monooxygenase activity in a pH‐dependent manner

“…Recently, LPMOs have been shown to also have roles in microbial pathogenicity [14,15], insect molting [16], and remodeling of the bacterial cell wall [17], indicating that LPMOs have several roles in Nature [18]. LPMOs are currently classified in eight Auxiliary Activity families (AA9-11, [13][14][15][16][17] in the Carbohydrate Active enZyme database [19].…”

“…The seminal 2010 study by Vaaje-Kolstad et al [1] showing that LPMOs oxidatively cleave recalcitrant chitin sparked a widespread interest in both fundamental and applied aspects of these enzymes [11][12][13]. Recently, LPMOs have been shown to also have roles in microbial pathogenicity [14,15], insect molting [16], and remodeling of the bacterial cell wall [17], indicating that LPMOs have several roles in Nature [18]. LPMOs are currently classified in eight Auxiliary Activity families (AA9-11, [13][14][15][16][17] in the Carbohydrate Active enZyme database [19].…”

A fungal lytic polysaccharide monooxygenase is required for cell wall integrity, thermotolerance, and virulence of the fungal human pathogen Cryptococcus neoformans

“…Even though LPMOs were first described as enzymes involved in dead biomass recycling, they have been functionally linked to new roles such as cell morphogenesis. Additionally, for plant- and insect-targeting microbes, LPMOs are important effectors during commensalism and pathogenic interactions [ 23 , 54 – 58 ]. In these previous studies, LPMOs were shown to be secreted together with other CAZymes for degradation of the host cell wall to facilitate microbial invasion of the host.…”

A fungal lytic polysaccharide monooxygenase is required for cell wall integrity, thermotolerance, and virulence of the fungal human pathogenCryptococcus neoformans

“…In this way, LPMOs create nicks in flat biopolymer sheets to allow additional hydrolyzing enzymes to further saccharify carbohydrate structures [51,52]. Even though LPMOs were first described as enzymes involved in dead biomass recycling, they have been functionally linked to new roles such as copper import, cell morphology changes, as well as in cell-cell interaction during commensalism and pathogenic interactions, in particular for plant-and insect-targeting microbes [13,18,[53][54][55][56][57]. In these studies, LPMOs were shown to be secreted together with other CAZymes for degradation of the host cell wall to facilitate cellular invasion of the host by the microbe.…”