Diacylglycerol kinase alleviates autophagic degradation of the endoplasmic reticulum in SPT10-deficient yeast to enhance triterpene biosynthesis.

A recent study showed that deletion of the gene encoding the transcription regulator SuPpressor of Ty10 (SPT10) increases total phospholipids, and our previous study established a critical link between phospholipids and the mevalonate/ergosterol (MEV/ERG) pathway, which synthesises triterpenes. This study aims to use spt10Δ yeast to improve triterpene production. Though MEV/ERG pathway was highly expressed in spt10Δ yeast, results showed insufficient accumulation of key metabolites and also revealed massive endoplasmic reticulum (ER) degradation. We found a stable, massive ER structure when we overexpressed diacylglycerol kinase1 (DGK1OE ) in spt10Δ yeast. Analyses of ER-stress and autophagy suggest that DGK1OE in the spt10Δ strain decreased autophagy, resulting in increased MEV/ERG pathway activity. Heterologous expression of ß-amyrin synthase showed significant production of the triterpene ß-amyrin in DGK1OE spt10Δ yeast. Overall, our study provides a strategic approach to improve triterpene production by increasing ER biogenesis while limiting ER degradation.

Phylogenetic diversity and activity screening of cultivable Actinobacteria isolated from marine sponges and associated environments from the western coast of India.

The phylogenetic diversity of cultivable actinobacteria isolated from sponges (Haliclona spp.) and associated intertidal zone environments along the northern parts of the western coast of India were studied using 16S rRNA gene sequences. A subset of randomly selected actinobacterial cultures were screened for three activities, namely predatory behaviour, antibacterial activity and enzyme inhibition. We recovered 237 isolates from the phylum Actinobacteria belonging to 19 families and 28 genera, which could be attributed to 95 putative species using maximum-likelihood partition and 100 putative species using Bayesian partition in Poisson tree processes. Although the trends in the discovery of actinobacterial genera isolated from sponges were consistent with previous studies from different study areas, we provide the first report of nine actinobacterial species from sponges. We observed widespread non-obligate epibiotic predatory behaviour in eight actinobacterial genera and we provide the first report of predatory activity in Brevibacterium , Glutamicibacter , Micromonospora , Nocardiopsis , Rhodococcus and Rothia . Sponge-associated actinobacteria showed significantly more predatory behaviour than environmental isolates. While antibacterial activity by actinobacterial isolates mainly affected Gram-positive target bacteria with little or no effect on Gram-negative bacteria, predation targeted both Gram-positive and Gram-negative prey with equal propensity. Actinobacterial isolates from both sponges and associated environments produced inhibitors of serine proteases and angiotensin-converting enzyme. Predatory behaviour was strongly associated with inhibition of trypsin and chymotrypsin. Our study suggests that the sponges and associated environments of the western coast of India are rich in actinobacterial diversity, with widespread predatory activity, antibacterial activity and production of enzyme inhibitors. Understanding the diversity and associations among various actinobacterial activities - with each other and the source of isolation - can provide new insights into marine microbial ecology and provide opportunities to isolate novel therapeutic agents.