https://pages.htgaa.org/2026b/david-castillo/week-02-hw-genetic-design/index.htmlHTBAA Homework #2: Genetic Construct Architecture for The Electric Cob Project Clean-Gene Segregation & Monophenolic Activation in Heritage Maize (Zea mays everta) Student: David J. Castillo-Cornejo Course: How to Biomanufacture (Almost) Anything (HTBAA Fall 2026) Due Date: Tuesday September 29, by 2:30p ET Part 0: Set up in Kernel Workspace & Project Folder: HTBAA-2026 / castillo-electric-cob Repository Architecture: The project workspace contains the modular expression cassettes and vector backbone corresponding to the clean-gene binary vector pCambia-dLB-kanR-GFP (physical construct sourced via Addgene #223177, designed by Andreas Stürmer), partitioned into discrete functional parts (Promoter, UTR, CDS, Terminator, Border elements) for verification, codon-bias evaluation, and biosecurity screening. Part 1: Define Your Expression Target 1. Target Molecule & Functional Role Primary Target (mGFP5er): An engineered, thermotolerant Green Fluorescent Protein targeted to the endoplasmic reticulum via an N-terminal basic chitinase signal peptide and a C-terminal HDEL retention motif. In the Electric Cob somatic embryogenesis pipeline, mGFP5er serves as a non-destructive optical reporter to quantitatively map early transformation foci (days 7–21) in friable Type II callus cultures without sacrificing proembryogenic masses. Secondary Target (NPTII): Neomycin phosphotransferase II, an aminoglycoside 3’-phosphotransferase conferring resistance to Geneticin (G418) for selective enrichment. 2. Sequence Provenance & Database Identifiers Reporter Gene (mGFP5er): Derived from Aequorea victoria GFP, stabilized with S65T and V163A substitutions for dual-wavelength excitation (395 nm / 470 nm) and ER localization. Accession: NCBI GenBank U87974.1 / Addgene Vector #223177 Sequence Length: 783 bp (CDS including ER signal sequence and HDEL tetrapeptide) Selection Marker Gene (nptII): Transposon Tn5-derived aminoglycoside 3’-phosphotransferase. Accession: UniProt P00552 / NCBI V00618.1 Sequence Length: 795 bp 3. Living System & Host Chassis Transformation Host & Binary Delivery Chassis: Agrobacterium tumefaciens strain AGL1 (hypervirulent, recA-deficient succinamopine-type chromosomal background C58 carrying disarmed Ti plasmid pTiBo542). Final Expression Chassis: Heritage Popcorn Maize (Zea mays everta landraces), specifically friable embryogenic Type II callus and regenerating somatic plantlets. 4. Subcellular Localization & Product Destination Reporter (mGFP5er) — Lumen of the Endoplasmic Reticulum (ER): Cytoplasmic GFP frequently suffers from cellular aggregation, rapid vacuolar turnover, or mild phytotoxicity in monocot meristematic tissues. Retaining mGFP5er within the ER via the Arabidopsis thaliana basic chitinase signal peptide (cleaved post-translocation) and C-terminal HDEL anchor yields higher steady-state fluorescence intensity and avoids nucleocytoplasmic quenching. Selection Marker (NPTII) — Cytoplasm: NPTII phosphorylates incoming aminoglycosides (G418) directly in the cytosol prior to ribosomal inactivation. Part 2: Design Your Genetic Parts The construct operates as a modular T-DNA bipartite expression cassette framed by an engineered Double Left Border (dLB) architecture. This structure induces mechanical termination at the primary Left Border (LB1) for the clean target gene, while transcriptional read-through into LB2 captures the antibiotic selection marker, allowing Mendelian segregation in subsequent progeny generations.Hugoen