TITLE: Sanger Tree of Life HMW DNA Extraction: Automated Plant MagAttract v.2
AUTHORS: Maja Todorovic, graeme oatley, Caroline Howard

[DESCRIPTION]
This protocol describes the automated extraction of HMW DNA from cryogenically homogenised tissue samples from plants and fungi intended for long-read sequencing. It employs the Qiagen MagAttract HMW DNA extraction kit and the Thermo Fisher KingFisher™ Apex. This process is effective for a wide variety of plant species covered by the Tree of Life Programme. The output of this protocol is HMW DNA, which, depending upon yield and genome size of the species, can be directed towards either HMW DNA Pooling or HMW DNA Fragmentation: Diagenode Megaruptor®3 for LI HiFi. This protocol was adapted from Sanger Tree of Life HMW DNA Extraction: Automated Plant MagAttract v.1 to improve sample lysis, and was updated to Sanger Tree of Life HMW DNA Extraction: Automated Plant MagAttract v.3 to include a pre-shear SPRI of the HMW DNA extracted.


Acronyms
HMW: high molecular weight
SPRI: solid-phase reversible immobilisation
HiFi: high fidelity

[BEFORE_START]
Add 100% ethanol to MW1 and PE wash buffers as per manufacturer’s instructions.

[GUIDELINES]
For the lysis buffer master mix, prepare enough for n+1 samples to allow for pipetting errors.
Keep samples on dry ice to maintain temperature and prevent nucleic acid degradation until the lysis buffer is ready to be added to them.
An experienced operator can expect to comfortably process up to 32 samples, with approximately 2–3 hours handling time over a start to finish period of 4–5 hours. This estimation includes the utilisation of the KingFisher™ Apex and excludes subsequent QC checks.

Additional Notes:
FluidX tubes are used throughout the Tree of Life programme in order to track samples, therefore rather than the microcentrifuge tubes which have been mentioned in this protocol for DNA storage, all routine DNA extracts are stored in FluidX tubes.
Both the KingFisher™ Apex protocol script and the KFX.file have been made available for this protocol – the KFX.file requires ‘BindIx software for KingFisher Apex’ to allow the KingFisher™ Apex protocol to be viewed on a PC or laptop. Alternatively, the file can be transferred directly onto a KingFisher™ Apex instrument using a USB flash drive.

[STEPS]
SECTION: Sample lysis
1. Prepare a lysis buffer master mix:
  ReagentVolume per samplePhosphate buffered saline (PBS)200 µLProteinase K20 µLRNase A4 µLBuffer AL150 µL

SECTION: Sample lysis
2. Set a heat block to 55 °C.
SECTION: Sample lysis
3. Transfer 50 mg of cryogenically homogenised tissue from each sample to 2 mL microcentrifuge tubes and place on dry ice to keep the samples frozen.
SECTION: Sample lysis
4. Add 374 µL of the lysis buffer master mix to each sample, then homogenise sample and mastermix by gently pipetting 10 times with a wide-bore pipette tip.
SECTION: Sample lysis
5. Centrifuge tube briefly to collect, then incubate on the heat block at 55 °C at 600 rpm for 1 hour.
SECTION: Loading and Running the KingFisher™ Apex
6. While the samples are lysing, label nine 1 mL 96-well deep-well KingFisher™ plates and fill the number of wells required for the number of samples in each plate as follows:
  PlateReagent(s) requiredTip plate96-well tip comb (no reagent)Elution 2 200 µL Buffer AE Elution 1 200 µL Buffer AE NFW Wash 500 µL Nuclease-Free Water PE Wash 2700 µL Buffer PEPE Wash 1700 µL Buffer PEMW1 Wash 2700 µL Buffer MW1MW1 Wash 1700 µL Buffer MW1Sample plate15 µL Suspension G magnetic beads 280 µL Buffer MB

SECTION: Loading and Running the KingFisher™ Apex
7. Once samples have completed lysing, remove sample tubes from the heat block and briefly centrifuge to spin down.
SECTION: Loading and Running the KingFisher™ Apex
8. Using a wide-bore pipette tip, set the volume to 380 µL, transfer lysate from the sample tubes to individual wells in the sample plate, taking care not to transfer large pieces of debris if possible.
SECTION: Loading and Running the KingFisher™ Apex
9. Select the required protocol in the protocol list on the KingFisher™ Apex (details in KingFisher™ Apex DNA Extraction Protocol Script/attached KFX file in the Materials section) and select using the play button.
SECTION: Loading and Running the KingFisher™ Apex
10. Load the filled plates onto the instrument following the instructions provided on screen.
SECTION: Loading and Running the KingFisher™ Apex
11. Prior to loading the “Sample Plate”, the instrument will prompt to remove the “Tip Plate”. Once the final plate is loaded, the protocol will automatically begin; this takes approximately 50 minutes.
SECTION: Loading and Running the KingFisher™ Apex
12. Once the protocol has completed, follow the on-screen instructions to remove plates from the instrument.
SECTION: Loading and Running the KingFisher™ Apex
13. Inspect the elution plates for any magnetic beads in the wells. In the rare instance of magnetic beads remaining in the eluate (possible in viscous samples), these samples will need to be transferred to a 1.5 mL microcentrifuge tube and placed on a magnetic rack. Allow around 5 minutes for the beads to migrate and take the clear eluate containing the DNA using a wide-bore pipette tip.
SECTION: Loading and Running the KingFisher™ Apex
14. Using a 200 µL multi-channel pipette and wide-bore tips, pipette eluates from the elution plate into microcentrifuge tubes, pipette mix with wide-bore tips to fully homogenise DNA in the eluate.
SECTION: Loading and Running the KingFisher™ Apex
15. Perform required QC and then store the DNA at 4 °C.