Genetically Modified Sugarcane for Biofuels Production: Status and Perspectives of Conventional Transgenic Approaches, RNA Interference, and Genome Editing for Improving Sugarcane for Biofuels

Abstract

Sugarcane can produce sugar for world’s requirements of this sweetener, yield bioethanol to be used as vehicle fuel, generate electrical energy for export to the grid, and engender biodiesel for running heavy automobiles, simultaneously. Nevertheless, several constraints including impaired sugar production, high costs of second-generation biofuels, metabolic barriers and feedback controls, land and growth requirements, and biotic and abiotic stresses impede the role this incredible crop can play toward world’s energy matrix. Such obstacles have made it imperative to adopt transgenic approaches for surmounting the hitches and augment food as well as fuel production from sugarcane. Agrobacterium-mediated transformation has been apperceived as an efficient system for sugarcane transgenesis. Moreover, recent developments in next-generation sequencing, functional genomics, and genome editing have incremented the prospects of genetic manipulation of sugarcane through RNA interference and CRISPR/Cas, which are likely to boost the sugarcane’s share in the energy sector. Being a highly efficient photosynthesizer, huge biomass producer, and having an already established industry around the world, sugarcane is a promising crop for biofuel and bioenergy engenderment. Additional forms of sugar like isomaltose, apart from sucrose, have been expressed in sugarcane to breach the sucrose ceiling and repress its regulation mechanisms through transgenesis. Genetic modifications have also been recently strived to reduce lignin content in sugarcane cell wall, which is the major reason of extraordinarily high costs of second-generation bioethanol production. Moreover, efforts are also underway to yield lignocellulolytic enzymes required for digestion of lignocellulosic material of sugarcane inside the crop itself. Mix-stock concept is already maturing and cocktails of several enzymes have been expressed in sugarcane. Furthermore, there are also enormous prospects to produce biodiesel from sugarcane by introducing genes related to triacylglycerol production. Additionally, enhanced biomass production, improved cellulose accretion, transgenesis of energy cane, and biotic and abiotic stress tolerance are other potential ameliorations being targeted in sugarcane. Genetically modified sugarcane has been approved in Indonesia and Brazil for commercial cultivation, whereas field trials are in progress in Australia, Pakistan, and other cane-growing countries. It is anticipated that regulatory agencies would approve GM cane in other countries as well in near future. Therefore, transgenic sugarcane may be widely adopted by the industry to harvest maximum benefits from this phenomenal crop.