Termite Innate Digestive Enzymes
Termites are key organisms in tropical rainforests because of their role in decomposing lignocellulose and cycling carbon. Lignocellulose is the most abundant polymer on Earth and a major sink of atmospheric CO2. However, it is extremely recalcitrant and most organisms cannot fully utilise it. In the case of termites, they rely on both internal secretions and enzymes from their associated microbiome to break down this material.  It has been proposed that termite secretions are mainly confined to the midgut, the first section of the digestive system. Attached to the midgut are the labial glands, which secrete their contents into the labium. Although it has been proposed that these glands have a mainly defensive function, there are several gaps in our knowledge. The glands may serve as food markers and are associated with digestion in lower termite workers, while soldiers have more specialised secretions with defensive components.  In this study, we performed a transcriptomic comparison of these glands with the midgut in several termite species across the evolutionary spectrum. We focused on two castes, workers and soldiers. This study aims not only to better characterise the cellulose degradation genes expressed in both tissues, but also to disentangle their relative expression differences between castes. The current study will also provide deeper insights into different types of genes encoding enzymes or proteins with antimicrobial properties or related to the production of organic compounds such as, potentially, naphthalene. The potential applications of the knowledge generated here will be of paramount importance to industrial biotechnology.