#Sour – BioQuakes

Have you ever enjoyed an orange and wondered what causes its amazing citrus flavor? Well, scientists have recently discovered the origins of citrus’s sour taste.

Scientists have recently discovered the origins of citrus fruits like oranges and lemons. In their study, they discovered a specific gene, PH4, that influences the fruits’ taste by regulating the fruits’ citric acid levels. Additionally, the researchers traced the fruits’ evolutionary journey from the Indian subcontinent to south-central China over millions of years and discussed influences that environments may have had on the citrus.

There are many reasons why these fruits evolved the way they did. One reason discussed in the article is human interference through selective breeding. Thousands of years ago, humans selectively bred certain types of citrus for food and medicinal purposes. Another reason they might have evolved to have more citric acid is to prevent bacterial infections. Bacteria, generally, prefer neutral environments with a pH of about 7. o. Citric acid has a pH of about 3.2. Therefore, the more citric acid a fruit has the less likely bacteria can infect the fruit.

This relates to AP Bio through the involvement of genes in protein synthesis. During protein synthesis in a cell, the first thing that happens is transcription where information on the DNA is transcribed onto mRNA. The mRNA then is sent to the Rough Endoplasmic Reticulum where it is received on the cis face. There, on the ribosomes of the rough ER, the protein is synthesized. The type of protein that is synthesized here is determined by the information of the mRNA. Then the protein is sent to the Golgi where, based on the information from the mRNA, molecules are added to determine the final location of the protein. Genes, including PH4, are sections of DNA. Therefore, the PH4 gene, in part, determines what type of proteins are produced by the cell and where they go.

Wow! It is fascinating how a gene can influence an orange’s taste. I found this research so interesting because I love oranges. I wonder how other plants’ genes influence their taste?

Unlike the other four human tastes, our process of detecting sourness has always been a mystery, and scientists were definitely not expecting to find the answer in a protein normally found in the inner ear.

https://pxhere.com/en/photo/994259

This protein, coded by the gene scientists refer to as Otop1, usually functions as part of the vestibular system to maintain balance. Given this more commonly known function of the protein, scientists were shocked to find its use for both balance and detecting the acids often associated with sour taste. The association is actually not as far- fetched as one might think. Otop1 codes for the synthesis of calcium carbonate crystals which rest on the hairs of the inner ear and detect gravity to help humans stand upright. Researchers found that the tongue also uses these crystals to detect sour taste. Calcium carbonate, a relatively basic compound, dissolves when it comes into contact with acid, which reaction can be detected by the brain and interpreted as sour taste.

How could such a protein find its way to use in both our senses of balance and taste?

The answer lies in evolution. If a certain protein proves advantageous over generations, organisms with it in surplus may evolutionarily find other uses for the it. Recently scientists have actually found several proteins for sensory organs that double as homeostatic sensors in other tissues. Otop1 is only one of many; smell receptors are found in the kidney in surplus, as are sweet taste receptors in the bladder.

Although we have unearthed a lot about the human body over the years, there is always so much more to learn!

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: #Sour

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