Superior photosynthesis abilities of some plants could hold key to climate-resilient crops

Good news! Human ingenuity can handle climate change! Not all photosynthesis is created equal! This could be game changer!

Maybe C3 plants can easily be converted to C4 plants allowing for more efficient agriculture.

Keep in mind: Global warming is a hoax and climate change is a religion!

"More than 3 billion years ago, on an Earth entirely covered with water, photosynthesis first evolved in little ancient bacteria. In the following many millions of years, those bacteria evolved into plants, optimizing themselves along the way for various environmental changes. This evolution was punctuated around 30 million years ago with the emergence of a newer, better way to photosynthesize. While plants like rice continued using an old form of photosynthesis known as C3, others like corn and sorghum developed a newer and more efficient version called C4.

There are now more than 8,000 different C4 plant species, which grow particularly well in hot, dry climates and are some of the most productive crop species in the world. ...

Around 95% of plants use C3 photosynthesis, in which mesophyll cells—green spongy cells that live inside leaves—turn light, water, and carbon dioxide into plant-powering sugars. Despite its high prevalence, C3 photosynthesis has two major shortcomings: 

1) 20% of the time, oxygen is accidentally used instead of carbon dioxide and must be recycled, which slows down the process and wastes energy, and

2) pores on the leaf surface are open too frequently while waiting for carbon dioxide to enter, causing the plant to lose water and become more vulnerable to drought and heat.

Fortunately, evolution has solved these issues with C4 photosynthesis. C4 plants recruit bundle sheath cells, which normally serve as leaf vein support, to photosynthesize alongside mesophyll cells. As a result, C4 plants eliminate those oxygen-use mistakes to conserve energy and keep plant surface pores closed more often to conserve water. The result is a 50% increase in efficiency compared to C3 plants. ...

"We were surprised and excited to find that the difference between C3 and C4 plants is not the removal or addition of specific genes,” says Ecker. “Rather, the difference is on a regulatory level, which could make it easier for us in the long run to turn on more efficient C4 photosynthesis in C3 crops.” ...

When measuring gene expression in rice and sorghum plants, the scientists found that a transcription factor family commonly referred to as DOFs were in charge of turning on the genes to make bundle sheath cells in both species. They also noticed that DOFs were binding to the same regulatory element in both species. However, in C4 sorghum plants, this regulatory element was not only associated with bundle sheath identity genes—it was also turning on the photosynthesis genes. That suggested that C4 plants had at some point tacked ancestral regulatory elements for bundle sheath genes onto photosynthesis genes, so that DOFs would turn on both sets of genes at the same time. This would explain how bundle sheath cells in C4 plants gained the ability to photosynthesize.

These experiments revealed that both C3 and C4 plants contain the necessary genes and transcription factors required for the superior C4 photosynthesis process—a promising discovery for scientists hoping to nudge C3 plants to use C4 photosynthesis. ...

Next on the docket for the team is determining whether rice can be engineered to use C4 photosynthesis rather than C3. ..."

From the abstract:

"C4 photosynthesis is used by the most productive plants on the planet, and compared with the ancestral C3 pathway, it confers a 50% increase in efficiency. In more than 60 C4 lineages, CO2 fixation is compartmentalized between tissues, and bundle-sheath cells become photosynthetically activated. How the bundle sheath acquires this alternate identity that allows efficient photosynthesis is unclear. Here we show that changes to bundle-sheath gene expression in C4 leaves are associated with the gain of a pre-existing cis-code found in the C3 leaf. From single-nucleus gene-expression and chromatin-accessibility atlases, we uncover DNA binding with one finger (DOF) motifs that define bundle-sheath identity in the major crops C3 rice and C4 sorghum. Photosynthesis genes that are rewired to be strongly expressed in the bundle-sheath cells of C4 sorghum acquire cis-elements that are recognized by DOFs. Our findings are consistent with a simple model in which C4 photosynthesis is based on the recruitment of an ancestral cis-code associated with bundle-sheath identity. Gain of such elements harnessed a stable patterning of transcription factors between cell types that are found in both C3 and C4 leaves to activate photosynthesis in the bundle sheath. Our findings provide molecular insights into the evolution of the complex C4 pathway, and might also guide the rational engineering of C4 photosynthesis in C3 crops to improve crop productivity and resilience."

Superior photosynthesis abilities of some plants could hold key to climate-resilient crops - Salk Institute for Biological Studies "Salk scientists discover how some plant species evolved a more efficient photosynthesis approach; findings could help make crops like rice and wheat more resilient to climate change"

Exaptation of ancestral cell-identity networks enables C4 photosynthesis (open access)

Fig. 5: A cell-type-specific cistrome in C3 rice and C4 sorghum drives the partitioning of photosynthesis between mesophyll and bundle-sheath cells.

Cross sections of C3 rice (left) and C4 sorghum (right) shoots. Both grain crops evolved from a common ancestor, but sorghum evolved to photosynthesize more efficiently.