Last updated March 8, 2018 at 10:10 am
A super-fertile strain of sorghum produced accidentally in 2013 has now been fully sequenced, revealing the secret of how it doubles seed-production.
Sorghum (Sorghum bicolor) is a critically important cereal crop used for human and animal feed around the world. Its seeds are produced in clusters along multi-branched structures at the top of each stem.
However, in its natural state, each structure produces two types of flowers – sessile spikelets (SS) and pedicellate spikelets (PS) – and only the former produces a seed.
In 2013, however, a US Department of Agriculture researcher called Zhanguo Xin reported the creation of sorghum strain that doubled down on seed production by having fertile PS flowers.
Unfortunately, Xin was unable to determine just how he managed the feat. He had been using a technique known as chemical mutagenesis – a scattergun approach that involves exposing organisms to a range of chemical compounds in the expectation that the interaction will result in DNA mutations.
Such mutations are, by definition, random, and thus the precise alterations that occurred in the genome of Xin’s super plant, dubbed Sorghum bicolor multiseeded (msd), were unknown.
Until now. Writing in the journal Nature Communications, a team led by Xin reports that the difference between the high-yield mutants and standard sorghum lies in the production of an enzyme called jasmonic acid.
To make their finding, the scientists sequenced the entire genome of the plant and discovered a change to a protein coding gene known as MSD1. The change dramatically reduced the production of jasmonic acid in the msd variety, particularly during the early stages of flowering.
Subsequent experiments using standard sorghum established that high levels of the enzyme were responsible for preventing seed production in PS flowers.
“So, when the plant hormone is low, we get seeds set on every single one of the flowers,” says co-author Yinping Jiao.
“But when the plant hormone is high, we have a reduced number of fertile flowers, ending up in a reduced number of seeds.”
The discovery paves the way not only for the commercial production of high yield sorghum, but also for further research into increasing the fertility of other cereal crops, such as wheat and corn.