Improving Photosynthesis

choi

(1) Justin Gillis, Taking Aim at Hunger, by Altering Plant Genes. New York Times, Nov 18, 2016.
www.nytimes.com/2016/11/18/science/gmo-foods-photosynthesis.html

Quote:

(a) the first four paragraphs:

"URBANA, Ill — A decade ago, agricultural scientists at the University of Illinois suggested a bold approach to improve the food supply: tinker with photosynthesis, the chemical reaction powering nearly all life on Earth.

"The idea was greeted skeptically in scientific circles and ignored by funding agencies. But one outfit with deep pockets, the Bill and Melinda Gates Foundation, eventually paid attention, hoping the research might help alleviate global poverty.

"Now, after several years of work funded by the foundation, the scientists are reporting a remarkable result.

"Using genetic engineering techniques to alter photosynthesis, they increased the productivity of a test plant — tobacco — by as much as 20 percent, they said Thursday in a study published by the journal Science. That is a huge number, given that plant breeders [not using genetic engineering, of course] struggle to eke out gains of 1 or 2 percent with more conventional approaches.

(b) the principal investigator is professor "Stephen P Long, a crop scientist who holds appointments at the University of Illinois at Urbana-Champaign and at Lancaster University in England [because he was born, raised and earned his PhD in England]

(c) "For a decade, Dr Long [the English surname means a tall person] had argued that photosynthesis was not actually very efficient. In the course of evolution, several experts said, Mother Nature had focused on the survival and reproduction of plants, not on putting out the maximum amount of seeds or fruits for humans to come along and pick.

Note:
(a) Lancaster University
https://en.wikipedia.org/wiki/Lancaster_University
(officially known as the University of Lancaster; public; 1964- )
(b) Green Revolution
https://en.wikipedia.org/wiki/Green_Revolution
(The initiatives, led by Norman Borlaug [1914 – 2009; American plant biologist; PhD University of Minnesota], the "Father of the Green Revolution," who received the Nobel Peace Prize in 1970)
(c) "Barry D Bruce of the University of Tennessee at Knoxville"

University of Tennessee
https://en.wikipedia.org/wiki/University_of_Tennessee
(located in Knoxville; Founded in 1794, two years before Tennessee became the 16th state to enter the Union)
(d) There is no need to read the rest, because you are proceeding to the source.

choi

(2)
(a) Kromdijk J et al, Improving Photosynthesis and Crop Productivity by Accelerating Recovery from Photoprotection. Science, 354, 857-861 (Nov 17, 2016).
science.sciencemag.org/content/354/6314/857
(b) Erik Stokstad, How Turning off a Plant's Sunshield Can Grow Bigger Crops. Science, Nov 17, 2016 (blog).
www.sciencemag.org/news/2016/11/ ... n-grow-bigger-crops

Quote:

"Just because plants photosynthesize doesn't mean they can't get a form of sunburn—damage caused by overexposure to light. That's why all plants rely on a mechanism that defends against excessively bright sunlight by converting photons into harmless heat. But  * * * this botanical sun shield is slow to turn off when a shadow passes over a leaf. The result: Photosynthesis stays depressed.

"During the green revolution, for example, Norman Borlaug and others nearly doubled wheat yields by creating plants with short, sturdy stems that could hold a greater load of grain. Nowadays, breeders can get crops to put about 50% to 60% of their biomass into seeds. But the gains have stagnated at less than 1% per year because plant growth is now limited by the efficiency of photosynthesis itself.  Research teams are trying to break the bottleneck in multiple ways. One long-held dream is taking a high-power type of photosynthesis found in corn and three other crops, called the C4 pathway, and putting it into rice.

"To guard themselves from bright light * * * plants rely on a mechanism called nonphotochemical quenching (NPQ), in which chloroplasts divert photons from their light-harvesting molecules and simply waste them as heat. In dim conditions, plants can turn off NPQ to boost photosynthetic efficiency. But although they can raise the shield in a few minutes, lowering the defenses can take hours, which limits photosynthesis in the shade.  This time lag isn't a problem for wild plants, for which survival and reproduction are paramount, but it's a disadvantage for farmers who want to maximize biomass.

Note:
(i) Regarding "short, sturdy stems" in the second quotation. The short" part aims to divert plant resources from stem to seeds, and the "sturdy" part to ensure the stem will not break due to the now enormous mass of seeds.
(ii)
(A) There are three types are carbon fixation: CAM, C3 and C4.
(B) CAN stands for "Crassulacean acid metabolism."  

"The first time it was studied, Crassula
https://en.wikipedia.org/wiki/Crassula
was used as a model organism."  Wikipedia

Representative CAM plants are Crassula (name of a genus) and cactus.
(C) C3 pathway, in its first step, produces 3-phosphoglycerate (which has three carbon atoms).
(D) C4 pathway produces as the first product a 4-carbon compound: either malic acid or aspartic acid, and "is believed to have evolved more recently. * **  Marshall Davidson Hatch and CR Slack * * * elucidated it in Australia, in 1966."  Wikipedia
(iii)
(A) Virginia Berg, Plant Biology, University of Northern Iowa, Mar 4, 2009.
www.uni.edu/bergv/pp/unit_2/pp092-11.html

Quote:

"C4 plants are more efficient with water, but less efficient with light (so it needs more light)

"Where C3 and C4 predominate
C4: bright, dry, warm places (maize, sugar cane, many desert plants)
C3: cooler, wetter, cloudier

"Reminder:
* * *
C3 plants have C3 reactions only, in every green cell
C4 plants have C4 reactions in some cells, C3 reactions in others [at the same time]

"Examples * * *
C3
        beans, rice, wheat, potatoes
        most temperate crops
        all woody trees

C4
        corn, sugarcane, amaranth
        mostly grasses but some shrubs (cold-tolerant)

(iii) "After reading Long's paper, geneticist Krishna Niyogi of the University of California, Berkeley, had an idea for how to turn off NPQ faster. The strategy was to add extra copies of three genes whose proteins are responsible for relaxing the protection. The higher protein levels should speed the response to shade."

This says that tobacco plant has indigenous three genes of its own. Adding more copy of the ALMOST same genes (from another model plant, mustard, which is "widely studied") merely to boost the proteins, products of these three genes -- to hurry up the reactions of turning off the protection from sunburn.