Desnoyer, N. | Search bioRxiv

bioRxiv2026

AMBER and GOLD: Polycistronic Genes for Betaxanthin Production in Plants

Genetically encoded pigments are powerful visual reporters and creative tools for biology, yet in plants the palette of pigment biosynthesis genes has remained largely limited to red betacyanins encoded by RUBY. Here we develop and characterize three new polycistronic constructs AMBER_v1, AMBER_v2, and GOLD that contain betalain biosynthesis enzymes to produce yellow, fluorescent betaxanthins in plant tissues. These tools expand the palette of publicly available pigmentation genes for use in plant research, education, and floral design.

bioengineering↗

bioRxiv2024

The Pollen Tube Penetrates the Synergid Cell by Formation of a Peritubular Membrane

In flowering plants, successful reproduction relies on an exchange of signals between synergids and pollen tubes (PTs), mediating the invasion of a synergid by the PT, which then ruptures and releases two sperm cells to effect double fertilization. However, how exactly the PT invades the receptive synergid is unknown as the spatial relationship between these two cells is unclear. To better understand this process we performed 3D live imaging of PT reception in Arabidopsis thaliana. Upon arrival at the filiform apparatus (FA), a region rich in membrane folds at the micropylar pole of the synergids, the PT gradually deforms the FA before it rapidly grows into the receptive synergid. Upon penetration, the membrane of the receptive synergid invaginates and envelopes the PT. We termed this newly discovered structure the peri-tubular membrane (PRM). We show that, in feronia mutants disrupting PT reception, the PT still enters the receptive synergid, forming a normal PRM. This results in extensive invagination of the synergid membrane without sperm release. We show that PRM formation is associated with a cytosolic calcium ([Ca2+]cyt) spike of high amplitude in the PT and flooding of [Ca2+]cyt in the synergids. In PTs lacking AUTOINHIBITED Ca2+ ATPASE9 activity, PTs have lower amplitude [Ca2+]cyt spiking and the PTs frequently fail to penetrate the synergid. Our findings suggest that synergid penetration and the non-cell autonomous control of PT rupture are distinct regulated processes required for fertilization in flowering plants.

plant biology↗

bioRxiv2020

AtPIG-S, a predicted Glycosylphosphatidylinositol Transamidase Subunit, is critical for pollen tube growth in Arabidopsis

BackgroundGlycosylphosphatidylinositol (GPI) addition is one of the several post-translational modifications to proteins that increase their affinity for membranes. In eukaryotes, the GPI transamidase complex (GPI-T) catalyzes the attachment of pre-assembled GPI anchors to GPI-anchored proteins (GAPs) through a transamidation reaction. A mutation in AtGPI8 (gpi8-2), the putative catalytic subunit of GPI-T in Arabidopsis, is transmitted normally through the female gametophyte (FG), indicating the FG tolerates loss of GPI transamidation. In contrast, gpi8-2 almost completely abolishes male gametophyte (MG) function. Still, the unexpected finding that gpi8-2 FGs function normally requires further investigation. Additionally, specific developmental defects in the MG caused by loss of GPI transamidation remain poorly characterized. ResultsHere we investigated the effect of loss of AtPIG-S, another GPI-T subunit, in both gametophytes. Like gpi8-2, we showed that a mutation in AtPIG-S (pigs-1) disrupted synergid localization of LORELEI (LRE), a putative GAP critical for pollen tube reception by the FG, yet is transmitted normally through the FG. Conversely, pigs-1 severely impaired male gametophyte (MG) function during pollen tube emergence and growth in the pistil. A pPIGS:PIGS-GFP transgene complemented these MG defects and enabled generation of pigs-1/pigs-1 seedlings, but seemingly failed to rescue the function of AtPIG-S in the sporophyte, as pigs-1/pigs-1, pPIGS:PIGS-GFP seedlings died soon after germination. ConclusionsCharacterization of pigs-1 provided further evidence that the FG tolerates loss of GPI transamidation more than the MG and that the MG compared to the FG may be a better haploid system to study the role of GPI-anchoring. pigs-1 pollen develops normally and thus represent a tool in which GPI anchor biosynthesis and transamidation of GAPs have been uncoupled, offering a potential way to study free GPI in plant development. While previously reported male fertility defects of GPI biosynthesis mutants could have been due either to loss of GPI or GAPs lacking the GPI anchor, our results clarified that the loss of mature GAPs underlie male fertility defects of GPI-deficient pollen grains, as pigs-1 is defective only in the downstream transamidation step. Our study also provided further evidence that GPI transamidation is essential in seedling development.

plant biology↗