A project undertaken at The University of Queensland, and supervised by Dr Mengbai Zhang.
Nitrogen is an essential macronutrient for plant growth, with large quantities used in agriculture to maximise crop production. However, this high usage of nitrogen-based fertilisers has led to serious pollution problems around the world. Legumes include important crops, such as beans, peas and soybean, and help reduce nitrogen fertiliser inputs by acquiring nitrogen from the atmosphere via symbiosis with nitrogen-fixing soil-borne bacteria, called rhizobia. When cultivated in rotation with other crops, legumes improve soil fertility and can break the chain of disease transmission. Moreover, they represent a great source of high-quality plant protein and essential nutrients that are economical and nutritious. In 2022-2023, Australia produced 4.4 million tonnes of legume seed (pulses), and this contributed to a global market valued at AU$ ~2.9 billion (ABARES/ABS 2023).
The importance of legumes to human nutrition, the economy and the environment necessitates and furthers research efforts to generate new and superior legume varieties that exhibit favourable traits, such as high yield, disease/drought-resistant, increased protein content, etc. This can be achieved via traditional breeding programs but that is limited to the available genetic diversity. Today, highly targeted genome-editing technologies (e.g. CRISPR) can expediate the process and generate different version of genes not previously available. Importantly, new varieties can be generated that contain no foreign DNA and are thus not considered GMO in Australia. However, gene-edited plants are currently achieved through tissue culture, a time-consuming and resource-intensive process involving the hormonal induction of a whole plant from small pieces of plant tissues (e.g. leaf).
This project aims to develop a new method that can circumvent the rate-limiting steps mentioned above, thus accelerating the generation of CRISPR/Cas9-edited crop varieties. We will use well-established techniques developed in our lab, including the generation of transgenic roots to replace the original root system of a non-transformed legume plant. These hairy roots will harbor the necessary molecular components required for genome-editing at high frequency. They will be mobilised systematically within the plant such that editing of target genes can occur in cells that develop into seeds without inducing a change in the genomic background of the shoot.
The generation of hairy roots in many legume species is readily achievable within one month following inoculation with hairy root-inducing Agrobacteria. This indicates that transgene-free edited seeds can be obtained in a short time frame and within just one generation, which will potentially revolutionise the production of new and superior legume crop varieties that are transgene free and suitable for use in agriculture.