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In This Issue

Olive tree genome yields insights into oil biosynthesis

Olive tree. Image courtesy of Pixabay/Hans.

Cultivated varieties of olive trees are thought to have stemmed from oleaster (Olea europaea var. sylvestris), the wild precursor, in Asia Minor before reaching the Mediterranean, which serves as a home to an array of olive varieties. Turgay Unver et al. (pp. E9413–E9422) assembled and annotated the 1.48 Gbp draft genome sequence of oleaster, revealing signatures of ancient genetic events related to olive oil biosynthesis. Harboring an estimated 50,684 protein-coding genes, the oleaster genome exhibits signs of multiple ancient genome duplication events, notable among which are two events specific to the oleaster lineage that occurred around 28 and 59 million years ago. The pair of duplication events led to the expansion and functional diversification of genes involved in oil biosynthesis, potentially explaining the high content of oleic acid (75%), a major component in olive oil, compared with linoleic acid (5.5%); by comparison, the closely related sesame seed oil contains around 40% of each fatty acid. Reduced expression of FAD2 genes that results from naturally occurring RNA interference and heightened expression of SACPD genes through ancient gene duplication might together account for olive oil’s high oleic acid content. According to the authors, the draft genome sequence yields insights into the evolution of oil biosynthesis that could be applied to improve olive oil production. — P.N.

How gut microbes may trigger multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease in which immune cells destroy the myelin sheath, a material that surrounds and protects nerve cells in the brain and spinal cord. An altered gut microbiota is often observed in patients with MS, but it has not been clear how this condition, known as dysbiosis, contributes to the onset or progression of the disease. Sudhir Yadav et al. (pp. E9318–E9327) provide evidence that dysbiosis stimulates the development of pathogenic T cells, thereby initiating or exacerbating experimental autoimmune encephalomyelitis (EAE)—an animal model of MS. The authors engineered mice to carry genes that trigger the spontaneous development of EAE. Compared with control mice, EAE-prone mice had higher fecal levels of immunoglobulin M (IgM)—a host antibody produced in response to dysbiosis. Higher fecal IgM levels were associated with increased intestinal permeability, elevated blood levels of bacterial toxins, and upregulated expression of the autoimmunity-related gene complement C3 in the spleen. Moreover, the expression of genes for Foxp3 and E3 ubiquitin ligase was reduced in mice with higher fecal levels of IgM, triggering the development of pathogenic T cells thought to initiate autoimmunity. Dysbiosis might induce the release of microbial toxins, which stimulate the host’s immune system to attack the myelin sheath, thereby contributing to the initiation or progression of MS, according to the authors. — J.W.

Wolves, dogs, and cooperation

Wolves working at a cooperative rope-pulling test. Image courtesy of Rooobert Bayer (Wolf Science Center, Ernstbrunn, Austria).

Previous studies suggest that domestication may have led dogs to evolve tolerance and cooperation. However, wolves display a greater variety of cooperative behaviors than dogs, including group hunting, pup rearing, and territorial defense. To compare cooperative traits of dogs and wolves, Sarah Marshall-Pescini et al. (pp. 11793–11798) tested how similarly raised wolves and dogs performed at a cooperative rope-pulling test, in which two animals could access food only if both pulled on separate rope ends simultaneously. Regardless of whether the animals had prior training on the apparatus, the wolves outperformed the dogs, with dog pairs succeeding at two of 472 attempts and wolf pairs succeeding at 100 of 416 attempts. Cooperation in wolves was strongest among partners of similar rank and with close social bonds. Furthermore, wolves were more likely to simultaneously manipulate the apparatus than dogs, an action that appeared to help the wolves grasp the necessary coordinated behavior. The authors suggest that dogs may avoid simultaneously pulling on the ropes to avoid conflict over a coveted resource. Rather than supporting the hypothesis that dogs evolved greater cooperative inclinations than wolves, the study suggests that the different social behaviors of the two species influence their capacity for cooperation and communication, according to the authors. — L.C.

Autophagy and antitumor immunity

Targeting autophagy inhibits tumor growth and increases NK cell infiltration into tumor bed.

Natural Killer (NK) cells play a crucial role in controlling tumors, and finding ways to increase their infiltration into tumors could improve NK-based immunotherapies. Takouhie Mgrditchian et al. (pp. E9271–E9279) report that targeting the autophagy gene BECN1 in melanoma tumors inhibits tumor growth and increases the infiltration of functional NK cells into BECN1-defective tumors, compared with tumors with functional BECN1. NK cell infiltration into the tumor bed was dependent on the transcriptional overexpression of the chemokine gene CCL5 because silencing CCL5 suppressed NK cell infiltration. Similar to BECN1, targeting other autophagy genes or pharmacologically inhibiting autophagy using chloroquine also induced the expression of CCL5 in melanoma cells. The mechanism of CCL5 upregulation involved the enhanced phosphorylation of its transcription factor, c-Jun, through impaired phosphatase PP2A catalytic activity and a corresponding increase in JNK phosphorylation. Clinically, the authors found a positive correlation between the expression of CCL5 and an NK cell marker in melanoma patients, as well as patient survival. According to the authors, targeting autophagy induces a decrease in melanoma tumor volume by enhancing the NK cell infiltration into the tumor bed. Therefore, the authors suggest, inhibiting autophagy in tumor cells represents an innovative strategy to improve NK-based immunotherapy. — S.R.

Online Impact

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