Exaptation of ancestral cell-identity networks enables C photosynthesis.

C photosynthesis is used by the most productive plants on the planet, and compared with the ancestral C pathway, it confers a 50% increase in efficiency. In more than 60 C lineages, CO fixation is compartmentalized between tissues, and bundle-sheath cells become photosynthetically activated. How the bundle sheath acquires this alternate identity that allows efficient photosynthesis is unclear.

Streamlined regulation of chloroplast development in the liverwort Marchantia polymorpha.

Chloroplasts develop from undifferentiated plastids in response to light. In angiosperms, after the perception of light, the Elongated Hypocotyl 5 (HY5) transcription factor initiates photomorphogenesis, and two families of transcription factors known as GOLDEN2-LIKE (GLK) and GATA are considered master regulators of chloroplast development. In addition, the MIR171-targeted SCARECROW-LIKE GRAS transcription factors also impact chlorophyll biosynthesis.

Plasmodesmal connectivity in C Gynandropsis gynandra is induced by light and dependent on photosynthesis.

In leaves of C plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C acids in mesophyll (M) cells and subsequent decarboxylation in the bundle sheath (BS). In C grasses, proliferation of plasmodesmata between these cell types is thought to increase cell-to-cell connectivity to allow efficient metabolite movement.

C gene induction during de-etiolation evolved through changes in cis to allow integration with ancestral C gene regulatory networks.

C photosynthesis has evolved by repurposing enzymes found in C plants. Compared with the ancestral C state, accumulation of C cycle proteins is enhanced. We used de-etiolation of C and C to understand this process.

Shedding light on AT1G29480 of -An enigmatic locus restricted to Brassicacean genomes.

A key feature of C Kranz anatomy is the presence of an enlarged, photosynthetically highly active bundle sheath whose cells contain large numbers of chloroplasts. With the aim to identify novel candidate regulators of C bundle sheath development, we performed an activation tagging screen with . The reporter gene used encoded a chloroplast-targeted GFP protein preferentially expressed in the bundle sheath, and the promoter of the C phosphopyruvate carboxylase gene from served as activation tag because of its activity in all chlorenchymatous tissues of .

Chloroplast development in green plant tissues: the interplay between light, hormone, and transcriptional regulation.

Chloroplasts are best known for their role in photosynthesis, but they also allow nitrogen and sulphur assimilation, amino acid, fatty acid, nucleotide and hormone synthesis. How chloroplasts develop is therefore relevant to these diverse and fundamental biological processes, but also to attempts at their rational redesign. Light is strictly required for chloroplast formation in all angiosperms and directly regulates the expression of hundreds of chloroplast-related genes.

Introduction of glucan synthase into the cytosol in wheat endosperm causes massive maltose accumulation and represses starch synthesis.

We expressed a bacterial glucan synthase (Agrobacterium GlgA) in the cytosol of developing endosperm cells in wheat grains, to discover whether it could generate a glucan from cytosolic ADP-glucose. Transgenic lines had high glucan synthase activity during grain filling, but did not accumulate glucan. Instead, grains accumulated very high concentrations of maltose.

Insights into the control of metabolism and biomass accumulation in a staple C4 grass.

This article comments on: . 2020. BIOMASS YIELD 1 regulates Sorghum biomass and grain yield via the shikimate pathway.

LIKE SEX4 1 Acts as a β-Amylase-Binding Scaffold on Starch Granules during Starch Degradation.

In Arabidopsis () leaves, starch is synthesized during the day and degraded at night to fuel growth and metabolism. Starch is degraded primarily by β-amylases, liberating maltose, but this activity is preceded by glucan phosphorylation and is accompanied by dephosphorylation. A glucan phosphatase family member, LIKE SEX4 1 (LSF1), binds starch and is required for normal starch degradation, but its exact role is unclear.

Variations in the Calvin-Benson cycle: selection pressures and optimization?

This article comments on: 2019. Metabolite profiles reveal inter-specific variation in operation of the Calvin–Benson cycle in both C and C plants. Journal of Experimental Botany , 1843–1858.

Plastidial NAD-Dependent Malate Dehydrogenase: A Moonlighting Protein Involved in Early Chloroplast Development through Its Interaction with an FtsH12-FtsHi Protease Complex.

Malate dehydrogenases (MDHs) convert malate to oxaloacetate using NAD(H) or NADP(H) as a cofactor. mutants lacking plastidial NAD-dependent MDH () are embryo-lethal, and constitutive silencing (1) causes a pale, dwarfed phenotype. The reason for these severe phenotypes is unknown.

Two Plastidial Coiled-Coil Proteins Are Essential for Normal Starch Granule Initiation in Arabidopsis.

The mechanism of starch granule initiation in chloroplasts is not fully understood. Here, we aimed to build on our recent discovery that PROTEIN TARGETING TO STARCH (PTST) family members, PTST2 and PTST3, are key players in starch granule initiation, by identifying and characterizing additional proteins involved in the process in chloroplasts. Using immunoprecipitation and mass spectrometry, we demonstrate that PTST2 interacts with two plastidial coiled-coil proteins.

Homologs of PROTEIN TARGETING TO STARCH Control Starch Granule Initiation in Arabidopsis Leaves.

The molecular mechanism that initiates the synthesis of starch granules is poorly understood. Here, we discovered two plastidial proteins involved in granule initiation in leaves. Both contain coiled coils and a family-48 carbohydrate binding module (CBM48) and are homologs of the PROTEIN TARGETING TO STARCH (PTST) protein; thus, we named them PTST2 and PTST3.