Tag: Metabolism

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Mistletoe

festive parasites
regulating virulence
to preserve their hosts

Mistletoe is a parasitic plant often found growing on hardwoods, such as apple trees. Whilst able to photosynthesize itself, the majority of a mistletoe plant’s water and nutrients are taken from its host, putting strain on the host plant.

The burden of parasitism can be particularly hard on the host when environmental conditions are tough, for instance during a drought. Research by Nabity et al. (2021), however, has shown that the desert mistletoe (Phoradendron californicum) is able to adjust the balance between autotrophy (the amount it obtains resources for itself through photosynthesis) and heterotrophy (the amount it takes resources from its host).

During dry periods the researchers found that desert mistletoe plants increased the amount of photosynthesis they performed, limiting the burden they place on their environmentally stressed host, the velvet mesquite (Prosopsis velutina). In this way mistletoe plants increase the chances of their host plants surviving the harsh environmental conditions and, as a result, increase their own chances of survival.

The researchers also demonstrated evidence of competition for xylem resources between mistletoe plants on the same host, some of the first evidence of intraspecific competition in parasites. The mistletoe plants are able to detect other mistletoe plants on the same host and can adjust their virulence accordingly. Possible ways that mistletoe could detect one another include via scent (chemical compounds released through a plant’s pores) or through chemical compounds traveling along the host’s xylem.

The research also suggests that levels of relatedness between mistletoe plants sharing the same host may even affect virulence. More research is needed to clarify this, however, and to investigate whether the plants can actually detect relatedness or whether mistletoe’s method of seed dispersal simply means that plants sharing the same host are likely to have higher levels of relatedness than mistletoe plants on separate hosts.

Further reading: http://dx.doi.org/10.1016/j.cub.2021.01.034

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On a knife edge

Life on a knife edge:

The metabolic demands

facing polar bears.

 

Polar bears rely on marine mammals such as seals which are high-fat prey. Despite the richness of their diet however, new research suggests that a reduction in the prey availability can have severe consequences on polar bear survival.

Pagano et al (2018) monitored nine free-ranging female polar bears over 2 years, measuring their metabolic rates, daily activity patterns, body condition and foraging success. They found that more than half of the bears had an energy deficit resulting from a high metabolic rate (1.6 times higher than previously assumed) and a low intake of the high-fat prey. As fragmentation of sea ice continues and seals become harder to catch the high metabolic requirements of polar bears is likely to become increasingly catastrophic for the species.

Original research: https://doi.org/10.1126/science.aan8677

 

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Alchemist goldfish

Alchemist goldfish

change acid to alcohol

through doubled proteins.

 

Many species of carp (including goldfish) can survive for months over winter in frozen lakes despite a lack of oxygen. Without oxygen they use anaerobic respiration resulting in the production of lactic acid. To avoid a deadly build up of lactic acid the fish convert it into ethanol which diffuses across their gills into the surrounding water.

Researchers have now discovered how the fish do this. During energy production in the absence of oxygen a mutated set of proteins switches the metabolic pathway within mitochondria to produce ethanol instead. The fish have two sets of these proteins, one set which is very similar to that found in other species and one set that appears to be a duplicate of the first. These sets of proteins appear to have arisen during a whole genome duplication event approximately 8 million years ago and have enabled the fish to survive in conditions other species can’t. Fagernes et al, 2017.