A low CO2-responsive mutant of Setaria viridis reveals that reduced carbonic anhydrase limits C4 photosynthesis.

In C4 species, β-carbonic anhydrase (CA), localized to the cytosol of the mesophyll cells, accelerates the interconversion of CO2 to HCO3-, the substrate used by phosphoenolpyruvate carboxylase (PEPC) in the first step of C4 photosynthesis. Here we describe the identification and characterization of low CO2-responsive mutant 1 (lcr1) isolated from an N-nitroso-N-methylurea- (NMU) treated Setaria viridis mutant population. Forward genetic investigation revealed that the mutated gene Sevir.

Single Base Editing Using Cytidine Deaminase to Change Grain Size and Seed Coat Color in Rice.

The fast-moving CRISPR technology has allowed plant scientists to manipulate plant genomes in a targeted manner. So far, most of the applications were focused on gene knocking out by creating indels. However, more precise genome editing tools are demanded to assist the introduction of functional single nucleotide polymorphisms (SNPs) in breeding programs.

Re-creation of a Key Step in the Evolutionary Switch from C to C Leaf Anatomy.

The C photosynthetic pathway accounts for ∼25% of primary productivity on the planet despite being used by only 3% of species. Because C plants are higher yielding than C plants, efforts are underway to introduce the C pathway into the C crop rice. This is an ambitious endeavor; however, the C pathway evolved from C on multiple independent occasions over the last 30 million years, and steps along the trajectory are evident in extant species.

CRISPR-Cas9 and CRISPR-Cpf1 mediated targeting of a stomatal developmental gene EPFL9 in rice.

CRISPR-Cas9/Cpf1 system with its unique gene targeting efficiency, could be an important tool for functional study of early developmental genes through the generation of successful knockout plants. The introduction and utilization of systems biology approaches have identified several genes that are involved in early development of a plant and with such knowledge a robust tool is required for the functional validation of putative candidate genes thus obtained. The development of the CRISPR-Cas9/Cpf1 genome editing system has provided a convenient tool for creating loss of function mutants for genes of interest.

Targeted Knockdown of GDCH in Rice Leads to a Photorespiratory-Deficient Phenotype Useful as a Building Block for C4 Rice.

The glycine decarboxylase complex (GDC) plays a critical role in the photorespiratory C2 cycle of C3 species by recovering carbon following the oxygenation reaction of ribulose-1,5-bisphosphate carboxylase/oxygenase. Loss of GDC from mesophyll cells (MCs) is considered a key early step in the evolution of C4 photosynthesis. To assess the impact of preferentially reducing GDC in rice MCs, we decreased the abundance of OsGDCH (Os10g37180) using an artificial microRNA (amiRNA) driven by a promoter that preferentially drives expression in MCs.