Prospects of Gene Editing Techniques in Manipulating the Rhizosphere Microbiome for Millets Productivity

Abstract

Millets are a group of important drought-resistant “nutri-cereals” commonly cultivated in arid and semi-arid areas. A renewed focus on increasing their production and highlighting nutritional benefits is critical for promoting diverse diets and ensuring climate and food-nutritional security. Although millets are comparatively more climate-resilient than other cereals, their growth and production are frequently hindered by prolonged exposure to several abiotic and biotic stresses. In this line, improved millet varieties can be developed through various simple yet precise genome editing techniques. Targeted editing of the plant genomes not only expands our knowledge of the fundamental basis of plant physiology but also provides an opportunity for improving productivity and quality of crops. In addition, the rhizospheric plant–microbe interactions can also be explored toward formulating sustainable agricultural practices under challenging environments. The rhizosphere is plausibly the most complex interface facilitating the dynamic interactions between a plethora of microbial entities and plant roots. The microbial assemblages of millets consist of many plants’ growth-promoting rhizobacteria such as N₂-fixers, mineral (phosphate and zinc) solubilizers, anti-pathogenic bacteria, arbuscular mycorrhizal fungi, etc. The association of this microbial population with millet plants confers direct or indirect resistance to several abiotic (drought, salinity, heat, cold, oxidation, etc.) and biotic stresses (insects attacks, soil-borne phytopathogens), also modulates rhizoexudation, root architecture, plant biometry, and phenology. As such, elucidating the microbial diversity, deciphering and managing their biological functions will help in harnessing plant–microbe cross-talks toward increasing ecosystem services, plant plasticity, and productivity under environmental perturbations. Advances in gene editing techniques such as CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/Cas9), ZFN (zinc finger nucleases), TALENS (transcription activator-like effector nucleases), base editing, prime editing, etc. allow us to untangle the web of plant–microbe interaction as well as to improve nutritional qualities and stress tolerance of crops. Since studies on rhizosphere microbiota structure associated with millets are scanty, most of our understanding in genome-editing techniques has been derived from non-millet plants. In this chapter, we focused on how mechanistic understanding of various genome-editing technologies can be leveraged for the manipulation of susceptible genes and increase the plant’s fitness under diverse ecosystems.