Targeted Knockdown ofGDCHin Rice Leads to a Photorespiratory-Deficient Phenotype Useful as a Building Block for C₄Rice

Abstract

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. GDC H- and P-proteins were undetectable in leaves of gdch lines. Plants exhibited a photorespiratory-deficient phenotype with stunted growth, accelerated leaf senescence, reduced chlorophyll, soluble protein and sugars, and increased glycine accumulation in leaves. Gas exchange measurements indicated an impaired ability to regenerate ribulose 1,5-bisphosphate in photorespiratory conditions. In addition, MCs of gdch lines exhibited a significant reduction in chloroplast area and coverage of the cell wall when grown in air, traits that occur during the later stages of C4 evolution. The presence of these two traits important for C4 photosynthesis and the non-lethal, down-regulation of the photorespiratory C2 cycle positively contribute to efforts to produce a C4 rice prototype.

A phosphoproteomic landscape of rice (Oryza sativa) tissues

“…As an important enzyme of the photorespiration, the mitochondrial glycine decarboxylase complex (GDC) catalyzes the conversion of glycine, NAD + and tetrahydrofolate to CO 2 , ammonia, NADH and Methylenetetrahydrofolate (CH 2 ‐THF). Previous study demonstrated that knock‐down of the GDC subunit H (OsGDCH) led to photorespiratory‐deficient phenotypes with stunted growth, accelerated senescence, reduced chlorophyll, soluble protein and sugars in leaves, indicating the key roles of OsGDCH in rice photorespiration (Lin et al ). Meanwhile, psbS1 is a photoprotective protein controlling CO 2 assimilation rate in fluctuating light in rice (Hubbart et al ).…”

Temporal responses of conserved miRNAs to drought and their associations with drought tolerance and productivity in rice

“…Based on our prediction, approximately~14.2% of miRNAs (30 out of 211) can have potential negative pleiotropic effects on GDP. For instance, OsmiRNA439(a-i) negatively regulates OsGDCH (LOC_Os10g37180, PCC = -0.624) [26] while it positively regulates OsPIN5b (LOC_Os08g41720, PCC = 0.653) [30]. Moreover, OsmiRNA439(a-i) positively regulates OsNAC5 (LOC_Os11g08210, PCC = 0.569) [19] and OsALDH10A5 (LOC_Os04g39020, PCC = 0.582) [39], which act as positive regulators in DT.…”

Genetic Engineering for Global Food Security: Photosynthesis and Biofortification

“…The formation and recycling of 2PG comes at a cost, impacting on photosynthetic efficiency and therefore negatively impacting yield potential [1,[48][49][50][51][52][53][54][55]. A number of previous studies have shown that a reduction in photorespiratory flux under high photorespiratory conditions (i.e., high temperature or water stress) results in an overall reduction in photosynthetic efficiency and CO 2 assimilation [56][57][58][59]. In contrast, green tissue-specific overexpression of the glycine decarboxylase (GDC) H-protein or L-protein has been shown to increase vegetative biomass in Arabidopsis and tobacco [42,[60][61][62][63].…”