Diving Deeper: Unravelling How Plants Regulate Root Growth Angle
Lead Research Organisation:
University of Nottingham
Department Name: Sch of Biosciences
Abstract
Limited water and nutrient availability are the major constraints for global crop production and food security. These constraints are intensifying over time given the impact of climate change on water availability and the drive to reduce fertiliser inputs to make agriculture more environmentally sustainable. Therefore, developing crops with improved nutrient and water capture efficiency could provide the solution to make significant improvements in stress resilience and yields in our crops to meet the food demand of an increasing world population. In this context, root angle is a promising root architectural trait as it critically influences nutrient and water capture from different soil profiles. For instance, steeper root angle accesses mobile water and nitrogen from deeper soils, while shallow root angle improves capture of immobile phosphorous from topsoil.
Crop root systems include different root types (such as primary, seminal, lateral and crown), which grow at different angles to efficiently capture resources from different soil profiles. These different root angles are determined by gravitropic and anti-gravitropic offset (AGO) mechanisms. Previous research has uncovered many genes involved in gravitropic response machinery, however such knowledge about AGO mechanism is limited. To bridge this gap, we recently identified a novel gene (called Enhanced Gravitropism 1 i.e., EGT1) involved in AGO mechanism. A mutation within this gene causes all root types to grow only vertically downwards as it hinders their ability to maintain different growth angles. Our research further identified that mutant roots are defective in mainly two biological processes called as reactive oxygen species (ROS) maintenance and cell wall stiffness. As ROS levels in the root are known to determine cell wall's stiffness or looseness, we proposed a new AGO mechanism that EGT1 gene regulates ROS dependant cell wall stiffness to control root angle in different root types (Fusi et al., 2022. PNAS).
In this BBSRC New Investigator grant we will investigate the proposed AGO mechanism in barley roots to determine how it allows different root types to grow and capture water and nutrients efficiently from different soil profiles. We will first determine where in the root (specific tissues and growth zones) EGT1 gene is transcribed and the protein is made and accumulates. We will then express EGT1 specifically in these tissues and zones in the egt1 mutant (called complementation) to confirm tissue and zone predominantly required for EGT1 function. Next, we will determine how EGT1 controls downstream targets involved in ROS and cell wall stiffness processes. Finally, we will grow the wildtype, mutant and tissue and zone-specific complementation lines under water, nutrient and high temperature stress conditions to understand how this AGO mechanism is used by plant to change root angle in response to these conditions. We will also uncover whether change in angle in the mutant vs wildtype and complementation line roots are better able to grow under these abiotic stress conditions.
The knowledge gained in this study will provide vital new information about EGT1 and its key downstream targets involved in AGO mechanism and controlling root angle in response to environmental cues. This will help breeders to design novel approaches to enhance resource capture and improve yield in crops, supporting efforts to improve food security in the UK and worldwide. The remit of our project thus falls under a strategic priority area supported by the BBSRC Bioscience for Sustainable Agriculture and Food.
Crop root systems include different root types (such as primary, seminal, lateral and crown), which grow at different angles to efficiently capture resources from different soil profiles. These different root angles are determined by gravitropic and anti-gravitropic offset (AGO) mechanisms. Previous research has uncovered many genes involved in gravitropic response machinery, however such knowledge about AGO mechanism is limited. To bridge this gap, we recently identified a novel gene (called Enhanced Gravitropism 1 i.e., EGT1) involved in AGO mechanism. A mutation within this gene causes all root types to grow only vertically downwards as it hinders their ability to maintain different growth angles. Our research further identified that mutant roots are defective in mainly two biological processes called as reactive oxygen species (ROS) maintenance and cell wall stiffness. As ROS levels in the root are known to determine cell wall's stiffness or looseness, we proposed a new AGO mechanism that EGT1 gene regulates ROS dependant cell wall stiffness to control root angle in different root types (Fusi et al., 2022. PNAS).
In this BBSRC New Investigator grant we will investigate the proposed AGO mechanism in barley roots to determine how it allows different root types to grow and capture water and nutrients efficiently from different soil profiles. We will first determine where in the root (specific tissues and growth zones) EGT1 gene is transcribed and the protein is made and accumulates. We will then express EGT1 specifically in these tissues and zones in the egt1 mutant (called complementation) to confirm tissue and zone predominantly required for EGT1 function. Next, we will determine how EGT1 controls downstream targets involved in ROS and cell wall stiffness processes. Finally, we will grow the wildtype, mutant and tissue and zone-specific complementation lines under water, nutrient and high temperature stress conditions to understand how this AGO mechanism is used by plant to change root angle in response to these conditions. We will also uncover whether change in angle in the mutant vs wildtype and complementation line roots are better able to grow under these abiotic stress conditions.
The knowledge gained in this study will provide vital new information about EGT1 and its key downstream targets involved in AGO mechanism and controlling root angle in response to environmental cues. This will help breeders to design novel approaches to enhance resource capture and improve yield in crops, supporting efforts to improve food security in the UK and worldwide. The remit of our project thus falls under a strategic priority area supported by the BBSRC Bioscience for Sustainable Agriculture and Food.
Technical Summary
Root angle is a key trait for efficient capture of soil resources like nutrients and water. Different root classes in crops grow at distinct growth angles, which are determined by competing gravitropic and anti-gravitropic offset (AGO) mechanisms. Contrary to the detailed understanding of root gravitropic response, the AGO mechanism remains largely unexplored. To address this knowledge gap, we identified a novel barley mutant enhanced gravitropism1 (egt1) that disrupts AGO mechanism, causing all roots to grow steeper. We discovered that EGT1 functions (likely in a tissue- and zone-specific manner) as part of a novel AGO mechanism involving Reactive Oxygen Species (ROS) homeostasis and cell wall stiffening processes to control root angle (Fusi et al., 2022. PNAS).
'Diving Deeper' project will investigate this proposed AGO mechanism to determine how it enables different root classes to explore and capture resources efficiently from different soil profiles. EGT1 dual transcription and translational reporter line will be generated to monitor EGT1 expression and accumulation in root tissues and zones. Selected tissue- and zone-specific promoters (identified using single cell RNA sequencing) will be used to complement EGT1 expression in the egt1 CRISPR mutant to determine precise location of EGT1 function. Innovative molecular and omics approaches will be used to determine how EGT1 regulates downstream targets, including involved in ROS and cell wall stiffening processes. Finally, we will study reporter, mutant and complementation lines generated in this study under selected abiotic stresses to understand how this validated AGO mechanism is employed to alter root angle and its relevance in conferring stress resilience.
Improved understanding of genes and mechanisms controlling root angle will facilitate breeding of crop varieties better suited for resource capture and for sustainably burying carbon in deeper layers to mitigate the global carbon burden.
'Diving Deeper' project will investigate this proposed AGO mechanism to determine how it enables different root classes to explore and capture resources efficiently from different soil profiles. EGT1 dual transcription and translational reporter line will be generated to monitor EGT1 expression and accumulation in root tissues and zones. Selected tissue- and zone-specific promoters (identified using single cell RNA sequencing) will be used to complement EGT1 expression in the egt1 CRISPR mutant to determine precise location of EGT1 function. Innovative molecular and omics approaches will be used to determine how EGT1 regulates downstream targets, including involved in ROS and cell wall stiffening processes. Finally, we will study reporter, mutant and complementation lines generated in this study under selected abiotic stresses to understand how this validated AGO mechanism is employed to alter root angle and its relevance in conferring stress resilience.
Improved understanding of genes and mechanisms controlling root angle will facilitate breeding of crop varieties better suited for resource capture and for sustainably burying carbon in deeper layers to mitigate the global carbon burden.
