Cytokinins: A Genetic Target for Increasing Yield Potential in the CRISPR Era

Abstract

Over the last decade, remarkable progress has been made in our understanding the phytohormones, cytokinin’s (CKs) biosynthesis, perception, and signalling pathways. Additionally, it became apparent that interfering with any of these steps has a significant effect on all stages of plant growth and development. As a result of their complex regulatory and cross-talk interactions with other hormones and signalling networks, they influence and control a wide range of biological activities, from cellular to organismal levels. In agriculture, CKs are extensively used for yield improvement and management because of their wide-ranging effects on plant growth, development and physiology. One of the primary targets in this regard is cytokinin oxidase/dehydrogenase (CKO/CKX), which is encoded by CKX gene, which catalyses the irreversible degradation of cytokinin. The previous studies on various agronomically important crops indicated that plant breeders have targeted CKX directly. In recent years, prokaryotic clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system has been increasingly used in editing the CKO/CKX gene and phenomenal results have been achieved. This review provides an updated information on the applications of CRISPR-based gene-editing tools in manipulating cytokinin metabolism at the genetic level for yield improvement. Furthermore, we summarized the current developments of RNP-mediated DNA/transgene-free genomic editing of plants which would broaden the application of this technology. The current review will advance our understanding of cytokinins and their role in sustainably increase crop production through CRISPR/Cas genome editing tool.

Cytokinin biosynthesis in cyanobacteria: Insights for crop improvement

“…Cytokinins can be inactivated or degraded through an enzyme known as cytokinin dehydrogenase (CKX) (Zhang et al, 2021;Mandal et al, 2022) which catalyzes an irreversible, oxidative cleavage of the cytokinin side-chain, which regulates the concentration of active cytokinins in plants. Multiple CKX proteins are found in terrestrial plants, each with its own tissue and subcellular localization as well as substrate specificity.…”

“…Extensive research studies are being carried out in order to generate transgenic plants with enhanced stress resistance. Hereafter, the present article explains the overview of the genetic manipulation strategies for refinement of the plant's responses to various abiotic stressors, such as DNA methylation, post-transcriptional modification of mRNA, posttranslational modifications, tagging RNA molecules, micro-RNAs, epigenetic modification, and CRISPR-Cas9 editing (Mandal et al, 2022). Furthermore, the synthetic biology technologies and approaches will expand the capabilities and perspectives of genetic engineering initiatives aimed at improving the abiotic stress tolerance in plants (Sargent et al, 2022).…”

“…Plant yield and productivity have long been thought to be affected by cytokinins, which regulate many aspects of plant growth and development. Genes involved in CK synthesis (ipt encoding isopentenyl transferase) and metabolism (CKX encoding cytokinin dehydrogenase and the genes of glucosyltransferases) are the main targets of CK engineering (Mandal et al, 2022).…”

“…Researchers have demonstrated that tools such as carbon nanotubes and the widely used CRISPR-Cas9 genetic editing might be used to efficiently change the plant's genetic material (Demirer et al, 2021). A wide variety of crops have been successfully modified using the CRISPR/Cas technique due to its precision, simplicity, and low cost (Mandal et al, 2022;Yan et al, 2022). Nanomaterialmediated gene editing now provides the benefits of species independence, ease of use, acceptable preservation of external nucleic acids, strong biocompatibility, high transformation efficiency, and the potential for plant regeneration (He et al, 2019).…”

Genome-Wide Analysis and Evolutionary Perspective of the Cytokinin Dehydrogenase Gene Family in Wheat (Triticum aestivum L.)

“…Besides, CKs are widely used for crop yield improvement/management because of their broader effects on plant growth/development and physiology. Applications of CRISPR-based gene-editing tools in manipulating cytokinin metabolism at the genetic level for yield improvement has been reported in literature (Mandal et al, 2022). Genome editing occurs via natural process of random mutagenesis, mostly through SNPs to improve yield (Songstad et al, 2017).…”