Distinct plastid fructose bisphosphate aldolases function in photosynthetic and non-photosynthetic metabolism in Arabidopsis

Abstract

Plastid metabolism is critical in both photoautotrophic and heterotrophic plant cells. In chloroplasts, fructose-1,6-bisphosphate aldolase (FBA) catalyses the formation of both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate within the Calvin-Benson cycle. Three Arabidopsis genes, AtFBA1-AtFBA3, encode plastidial isoforms of FBA, but the contributions of each isoform is unknown. Phylogenetic analysis indicates that FBA1 and FBA2 derive from a recently duplicated gene, while FBA3 is a more ancient paralog. The fba1 mutants are phenotypically indistinguishable from the wild type, while both fba2 and fba3 have reduced growth. We show that FBA2 is the major isoform in leaves, contributing most of the measurable activity. Partial redundancy with FBA1 allows both single mutants to survive, but combining both mutations is lethal, indicating a block of photoautotrophy. In contrast, FBA3 is expressed predominantly in heterotrophic tissues, especially the leaf and root vasculature, but not in the leaf mesophyll. We show that the loss of FBA3 affects plastidial glycolytic metabolism of the root, potentially limiting the biosynthesis of essential compounds such as amino acids. However, grafting experiments suggest that fba3 is dysfunctional in leaf phloem transport, and we suggest that a block in photoassimilate export from leaves causes the buildup of high carbohydrate levels and retarded growth.

Proximity labelling allows to study novel factors in chloroplast developmenta

“…Interestingly, upon submergence an ACO3-YFP fusion protein is detected also inside plastids (Meng et al, 2022). FBA1 is described as plastidial fructose-1,6-bisphosphate aldolase (Carrera et al, 2021) and EMB3119 is a putative ribose 5-phosphate isomerase displaying an embryo-lethal knock out phenotype (Meinke, 2019). Interestingly, EMB3119 has also been described as thioredoxin interacting protein (Marchand et al, 2006), which would provide an interesting link to CBSX2 in redox regulation (Yoo et al, 2011).…”

Complementary environmental analysis and functional characterization of a plastid diatom lower glycolytic-gluconeogenesis pathway

“…In plants, these include the synthesis of starch from glucose-6-phosphate (6), produced directly in the chloroplasts of leaves via the gluconeogenic conversion of glyceraldehyde-3-phosphate into glucose-6-phosphate; or in non-photosynthetic plastids (amyloplasts) found in root and other storage tissue via the uptake of cytoplasmic hexose phosphates (Fig. 1A) (7,8). Further metabolites are synthesised in the plastids from shorter-chain sugars, including: free fatty acids and lipids from acetyl-coA (9,10); aromatic amino acids (via the shikimate pathway), aspartate and lysine from phospho-enol-pyruvate (PEP); small hydrophic amino acids (alanine, leucine, valine) from pyruvate; serine and cysteine from 3-phosphoglycerate (9,(11)(12)(13); chlorophyll (via the tetrapyrrole pathway) from glutamate and carotenoids (via the nonmevalonate pathway) from pyruvate (14,15).…”

Comparative de novo transcriptome analysis of flower and root of Oliveria decumbens Vent. to identify putative genes in terpenes biosynthesis pathway

“…This product belongs to the cytochrome b6-f complex—which facilitates the electron transfer between photosystem I (PSI) and photosystem II (PSII)—and is responsible for state transfer and circular electron flow around the PSI ( Munekage et al, 2001 ; Jahns et al, 2002 ; Maiwald et al, 2003 ). Fructose-1,6-biphosphate aldolase (FBA) in chloroplast catalyzes the development of both sedoheptulose 1,7-bisphosphate and fructose 1,6-bisphosphate within the Calvin-Benson cycle ( Carrera et al, 2021 ). While the expression of the FBA1 gene is most important in the aerial part of the plant, FBA3 , its homolog, is expressed in the root ( Carrera et al, 2021 ).…”

“…Fructose-1,6-biphosphate aldolase (FBA) in chloroplast catalyzes the development of both sedoheptulose 1,7-bisphosphate and fructose 1,6-bisphosphate within the Calvin-Benson cycle ( Carrera et al, 2021 ). While the expression of the FBA1 gene is most important in the aerial part of the plant, FBA3 , its homolog, is expressed in the root ( Carrera et al, 2021 ). PSBO1 and PSBP1 genes play a role in the photosystem II regulatory processes ( Yi et al, 2005 ).…”