February 4, 2013 | 1 Comment
A team of plant geneticists at Cold Spring Harbor Laboratory (CSHL) has successfully demonstrated an idea they describe as a “simple hypothesis” for making significant increases in yields for field corn known as “maize” in the rest of the world. Field corn is the product used for animal feed, corn oil, ethanol, and synthesized high fructose corn sugar.
North America’s modern variants of the scientific named Zea mays plant is among the indispensable food crops that feeds and fuels billions of the planet’s people. As global population soars beyond 6 billion and heads for an estimated 8 to 9 billion by mid-century, efforts to boost yields of essential food crops takes on ever greater potential significance.
The new findings obtained by CSHL Professor David Jackson and colleagues have been published in Nature Genetics. The work is the product of the culmination of over a decade of research and creative thinking on how to perform genetic manipulations in corn that will have the effect of increasing the number of its seeds – that are called kernels.
Plant growth and development depend on structures called meristems – reservoirs in plants that consist of the plant version of stem cells. When prompted by genetic signals, cells in the meristem develop into the plant’s organs such as the leaves, stems and stalks and the flowers. Jackson’s team has taken an interest in how quantitative variation in the pathways that regulate plant stem cells contribute to a plant’s growth and yield.
Professor Jackson said, “Our simple hypothesis was that an increase in the size of the inflorescence (the part of the shoot of seed plants where flowers are formed) meristem – the stem-cell reservoir that gives rise to flowers and ultimately, after pollination, seeds – will provide more physical space for the development of the structures that mature into kernels.”
Dr. Peter Bommert, a former postdoctoral fellow in the Jackson lab, performed an analytical technique on several corn variants that revealed what scientists call quantitative trait loci (QTLs): places along the chromosomes that “map” to specific complex traits such as yield. The analysis pointed to a gene that Jackson has been interested in since 2001, when he was first to clone it: a corn gene called FASCIATED EAR2 (FEA2).
Not long after cloning the gene, Jackson had a group of gifted Long Island high school students, part of a program called “Partners for the Future”, perform an analysis of literally thousands of maize ears. Their task was to meticulously count the number of rows of kernels on each ear. It was part of a research project that won the youths honors in the Intel Science competition. Jackson, meantime, gained important data that now has come to full fruition.
The lab’s current research has now shown that by producing a weaker-than-normal version of the FEA2 gene – one whose protein is mutated but still partly functional – it is possible, as Jackson postulated, to increase meristem size, and in so doing, get a corn plant to produce ears with more rows and more kernels.
How many more? In two different crops of corn variants that the Jackson team grew in two locations with weakened versions of FEA2, the average ear had 18 to 20 rows and up to 289 kernels – as compared with wild-type versions of the same varieties, with 14 to 16 rows and 256 kernels. Compared with the latter figure, the successful FEA2 mutants had a kernel yield increase of some 13%.
Jackson said, “We were excited to note this increase was accomplished without reducing the length of the ears or causing fasciation (a kind of abnormal growth) – a deformation that tends to flatten the ears.” Both of those characteristics, which can sharply lower yield, are prominent when FEA2 is completely missing, as the team’s experiments also demonstrated.
Teosinte, the humble wild weed that Mesoamericans began to modify about 7000 years ago, beginning a process that resulted in the domestication of corn and other maize varieties such as sorghum, makes only 2 rows of kernels; elite modern varieties of the plant can already produce as many as 20.
A next step in the research is to cross-breed the “weak” FEA2 gene variant, or allele, associated with higher kernel yield with the best corn and maize lines used in today’s food crops to ask if it will produce a higher-yield plant.
Thirteen percent across the world’s corn and maize crop is an enormous number and would have a huge impact on prices. Geneticists are adding to thousands of years of plan modification with another very big jump. If the trait will breed in with similar results, it looks like it would be just in time.
Where else the research might go is up for speculation. Corn is a grass along with wheat and rice, two other major food crops. The 21st century doesn’t look like so much starvation is in store, food crops interchanging with fuel crops not withstanding.