AP Biology class blog for discussing current research in Biology

Tag: Corn

CRISP[ie]R Corn Kernels?

Corn is unique in the way that its genome is highly complex, thus causing it to be very difficult to edit those genes with technology such as CRISPR. CRISPR is an advanced technology that is used to find a specific portion of DNA in a cell and then it alters that piece of DNA. To learn more about CRISPR, click here.

CRISPR CAS9 technology

In a recent study at Cold Spring Harbor Laboratory, researchers attempted to modify the growth of stem cells and promotor regions in corn using CRISPR. Thousands of years ago, corn was just a plant covered in weeds that formed very few kernels on its surface. Through gene editing technologies, scientists were able to transform the hopeless plant into a delicious vegetable with juicer kernels bursting from all surfaces. To increase the number of corn kernels 0n the surface of the plant, Professor David Jackson along with Lei Liu worked in collaboration with Professor Madelaine Bartlett from the University of Massachusetts Amherst. They were one of the first groups to tackle the editing of corn’s complex set of DNA.

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We are currently learning in AP Biology how DNA is replicated and can be altered. In replication, DNA is first untwisted by a helicase enzyme. Similarly, CRISPR uses an enzyme called Cas9 that unzips the DNA. This allows for the newly created strand of RNA to be matched to the target DNA. The Cas9 then cuts the DNA strand which causes the cell to attempt and put the strand back together and this results in new genes being formed because the DNA sequence is altered. This is just like how in replication, the DNA polymerase adds nucleotides to an existing strand of DNA. This video also provides a great visual description of how CRISPR can edit existing genes.

Since corn is a plant, it consists of plant cells that have a much stronger cell wall than animal cells do. This makes it harder for the CRISPR to access the cell’s DNA and make edits. CRISPR can be used to disrupt genes and eliminate them, as well as help the promoter regions which activate the genes instead. Corn kernel development depends on the genes supporting stem cell growth. They experimented by targeting random areas of the promoter to see which part will change the number of kernels on the cob.

Ontario-Corn-field 03

As a veggie-lover myself, I am so glad that these new gene-editing procedures allow for fuller, juicier corn kernels. Not only is this beneficial to those who eat corn on the cob or choose to enjoy a moist slice of cornbread, but also to those who love to sit down with a big bowl of popcorn to watch a movie. If a vegetable with such complex genes as corn is able to be improved, imagine what the future holds for other plants yielding yummy additions to our diets!

Plant Therapists: Scientists help plants make the decision to regenerate rather than defend themselves after injury

Plants are very susceptible to injury in many forms. They can’t hide from a hungry bunny rabbit or invasive fungi. As humans, we have “fight or flight” instincts, but flight is a tall order for plants. Instead, they have “fight or fix” instincts. When damaged plants have two responses, to repair and regenerate or defend. New York University’s Center for Genomics and Systems Biology decided to perform a study on this known quality of plants.

The defense method is the production of specific compounds, but the scientists’ experiment focused on the regeneration response. “Breeding crops that more readily regenerate and can adapt to new environments is critical in the face of climate change and food insecurity” said NYU professor and leader of the study, Kenneth Birnbaum. The study was split into two parts a study, and an experiment.

Early corn crop

The goal of the study was to understand the relationship between regeneration and defense responses. Does one happen or the other? Can they occur simultaneously? Does affecting one response have a subsequent affect on the opposing response?

The Scientists studied two plants; Arabidopsis and corn. Arabidopsis is common used as a model organism by plant biologists, while corn is the America’s largest crop. The answers they found to the previously posed questions are as follows. In most cases, both responses happen simultaneously and neither are at full strength. When the Scientists manually affected one of the responses, the other response did increase in frequency as a result. As Marcela Hernández Coronado of Cinvestav in Mexico put it, “The ‘fight or fix’ responses seem to be connected, like a seesaw or scales — if one goes up, the other goes down. Plants are essentially hedging their bets after an attack,”

The scientists were able to narrow down the cause of varying level of each response to plant glutamate receptor-like (GLRs) proteins. These receptors are related to glutamate receptors found in the human brain; hence the title of “Plant Therapists”. They learned that these receptors are responsible for regulating regeneration response and in turn, increasing defense response.

Competitive inhibitorConsidering the relationship with neural receptors, the scientists used preexisting drugs meant for these relative receptors. They used neural antagonists to inhibit GLRs. The antagonists are competitive inhibitors, that bind to the active site of the receptor blocking reception of signal molecules. The limited activity of the GLRs made the plants decide to heavily favor regeneration as the signals telling it otherwise were blocked.

The scientists also studied “quadruple mutants” in comparison to normal plants. The plants with mutated GLR had an increased rate of regeneration, further proving the effects of GLR on regulating the ratio between the two responses. Overall however, the plants that were given the neural antagonists were more successful in increased regeneration than the quadruple mutants.



CRISPR Technology is Finding Its Place in the Agricultural Industry

CRISPR technology is now laying a foundation in the agricultural world, trying to help corn growers improve the speed, versatility, and output of their crops. It has been difficult to implement CRISPR technology thus far, as the cells walls of plants, at a microscopic level, are particularly tough to penetrate. Fundamentally, CRISPR “…consists of enzymatic scissors called Cas9 that a guide made from RNA shuttles to an exact place in a genome.” The difficulty with plants cells is that, in comparison to animal cells, the extra-rigid cell walls make it immensely difficult for the guide RNA (gRNA) and the Cas9 to reach their destination on the genome. In response to this problem researchers have come up with what is described as an “inelegant” solution to this problem where they “…splice […] CRISPR genes into a bacterium that can breach the plant cell wall or put them on gold particles and shoot them with what’s known as a gene gun.” Unfortunately, this method doesn’t work in the crucial corn varieties where it is needed. However, a team of researchers in North Carolina, Timothy Kelliher and Quideng Que of Syngenta, in Durham, North Carolina have come up with an even more ingenious solution to deal with the stubborn plant cell walls. Haploid induction “…allows pollen to fertilize plants without permanently transferring ‘male’ genetic material to offspring. The newly created plants only have a female set of chromosomes – making them haploid instead of the traditional diploid. Haploid induction itself can lead to increased breeding efficiency and higher yielding plants.” This same method has been found to work in wheat and even Arabidopsis, “…a genus of plants related to cabbage, broccoli, kale, and cauliflower.” Yet again, sadly, CRISPR faces another drawback as scientist not that “…if it were done in the field, the changes wouldn’t spread because the male genome in the pollen – which carries the CRISPR apparatus – disappears shortly after fertilization.” However, there is still much hope for CRISPR technology, and it is without a doubt that we are making big strides into the future with gene editing technology.

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