Unicamp group substantially increases plant stem by manipulating the activity of the ScGAI gene in transgenic lines
Despite international efforts in improvement, advances in agronomy and in the effective management of pests and diseases that affect sugarcane, the agricultural crop has shown limitations in the development of stalks. This physical limitation of the plant's stem has contributed to restricting the sucrose and biomass content that can be obtained from it for the production of sugar and cellulosic ethanol, experts in the field point out.
“Breaking this limitation on the development of sugarcane in a substantial way through conventional crop improvement [by crossing varieties] has been difficult,” he said. Marcelo Menossi, professor at the Department of Genetics, Evolution and Bioagents at the Institute of Biology (IB) at Unicamp, at FAPESP Agency.
Menossi, in collaboration with postgraduate students supervised by him and colleagues at the National Laboratory for Bioethanol Science and Biotechnology (CTBE), Sugar Research Australia and Martin Luther University Halle-Wittenberg in Germany, discovered that the answer to overcoming the sugarcane yield limitation barrier may lie in a gene called ScGAI.
In a study carried out during a project linked to the FAPESP Bioenergy Research Program (BIOEN), they found that ScGAI is a key molecular regulator of sugarcane growth and development.
By manipulating the activity of this gene in transgenic sugarcane lines developed in Australia, it was possible to substantially increase the stalk and cause changes in the allocation of carbon to the cultivar's structural and storage molecules, the researchers revealed in an article published in Journal of Experimental Botany.
“The sugarcane in which we altered the expression of the ScGAI gene developed much more quickly. This opens up the prospect of developing a variety of energy cane that matures faster and increases biomass production per unit of time,” said Menossi.
The discovery was derived from the doctoral work of Rafael Garcia Tavares, carried out at IB-Unicamp under the guidance of Menossi with FAPESP scholarship.
During the study, it was observed that the ScGAI gene mediates the regulation of some plant growth hormones commonly used in sugarcane crops, such as ethylene and gibberellins.
Used on a large scale to improve the growth and yield of many horticultural and agricultural crops, gibberellins accelerate sugarcane ripening by triggering the rapid degradation of DELLA proteins and preventing them from interacting with and degrading other proteins that stimulate plant growth.
“Unlike gibberellins, ethylene, which is usually applied to sugarcane fields during the sugarcane maturation phase, when the farmer does not want the plant to continue growing and accumulating leaves, but only to continue accumulating sucrose, stabilizes the DELLA protein and allows it to interact with and degrade other growth-promoting proteins,” explained Menossi. “This role of the DELLA protein as a sugarcane growth regulator, however, was still not very clear.”
Patenting of the manipulation method
In order to better understand the role of the DELLA protein as a regulator of sugarcane growth – especially in stalk development –, the researchers carried out an experiment in which they altered the expression of the ScGAI gene in lines of an Australian transgenic sugarcane variety. .
In some lines of transgenic sugarcane, the ScGAI gene was silenced in order to reduce the production of DELLA protein and prevent it from interacting with and degrading other proteins important for the plant's development.
In other transgenic plant lines, the gene was allowed to be overexpressed with the aim of increasing DELLA production and stabilizing it, in order to allow it to interact with and degrade other growth-promoting proteins.
Analyzes comparing plant growth after four months showed that transgenic sugarcane lines with overexpression of the ScGAI gene showed stunted growth, shorter internodes (buds) and impaired energy metabolism.
The plants whose gene was silenced were taller, had rapid elongation of the internodes, greater production of phytomers – a unit that comprises a nodule and an internode, their axillary buds and attached leaves – and greater allocation of carbon to the stem.
“The study clearly showed that the ScGAI gene is a fundamental component for the development of sugarcane and can be a target for genetic manipulation in order to interfere with the speed of plant growth and development by regulating the DELLA protein”, Menossi pointed out.
The researchers began the process of patenting the method of manipulating the ScGAI gene to increase the amount of DELLA protein in sugarcane and enable the plant to develop faster. The technology has already sparked the interest of two companies.
“The next step of the research is to carry out field trials to check if we can obtain the same results that we had with the cultivation of transgenic lines with the manipulated gene in a greenhouse,” said Menossi.
THE ARTICLE
The article ScGAI is a key regulator of cum development in sugarcane (doi: 10.1093/jxb/ery180), by Rafael Garcia Tavares, Prakash Lakshmanan, Edgar Peiter, Anthony O’Connell, Camila Caldana, Renato Vicentini, José Sérgio Soares and Marcelo Menossi, can be read at Journal of Experimental Botany em academic.oup.com/jxb/advance-article/doi/10.1093/jxb/ery180/4996041.
