# Update \`SeppReferenceTree\` to SILVA 138.1
**URL:** https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600
**Category:** User Support
**Created:** [August 31, 2021, 8:39pm UTC](https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600 "2021-08-31T20:39:22Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@crusher083](https://forum.qiime2.org/u/crusher083)
#### Post date: [August 31, 2021, 8:39pm UTC](https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600/1 "2021-08-31T20:39:22Z")
Hi, I've been trying to recreate a SeppReferenceTree steps from thread:
> [@Trouble generating SeppReferenceDatabase qza](https://forum.qiime2.org/t/trouble-generating-seppreferencedatabase-qza/16729):
>
> Hi! I'm new to qiime2, so I'm not sure if I'm having problems because I couldn't find instructions for importing/creating a SeppReferenceDatabase. Goal: Use a customized subset of Silva 138 NR99 for sepp fragment insertion. What I've done: Using arb, exported the aligned fasta for the high quality seqs I want to use, after trimming to just the relevant 16S region, and exported the corresponding tree. Followed [Siavash's steps](https://github.com/smirarab/sepp-refs/tree/master/silva) to clean up the tree, resolve polytomies, and re-estimate branch …
1. I downloaded `Exports/SILVA_138.1_SSURef_NR99_tax_silva_trunc.fasta` and `Exports/taxonomy/tax_slv_ssu_138.1.tre.gz` from last [SILVA release](https://www.arb-silva.de/no_cache/download/archive/release_138.1/).
2. Then I run `nw_topology -bI` to prepare the tree.
I am intrested in creating `SeppReferenceDatabase` for V4 region specifically.
For the moment I am particularly puzzled with masking step described [here](https://github.com/smirarab/sepp-refs/tree/master/silva).
- should I first filter reference sequences from SILVA to V4 region or do this masking step?
- how should I choose the masking length properly?
- should I take anything else into account to make the database reusable for community?
@dethlefs@hugh @Stefan your experience would be invaluable to accomplish this task.
Cheers!
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### Author:  [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [September 1, 2021, 2:07pm UTC](https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600/2 "2021-09-01T14:07:37Z")
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### Author:  [@lizgehret](https://forum.qiime2.org/u/lizgehret)
#### Post date: [September 1, 2021, 9:17pm UTC](https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600/5 "2021-09-01T21:17:27Z")
Hi @crusher083, welcome back to the :qiime2: forum!
Our [Data Resources](https://docs.qiime2.org/2021.4/data-resources/#sepp-reference-databases) linked from the user docs are going to be your best bet within QIIME 2 - if those don't address your questions, I'd recommend posing your questions in [GitHub - smirarab/sepp-refs](https://github.com/smirarab/sepp-refs/). Hope this helps!
Cheers,
Liz
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### Author:  [@lizgehret](https://forum.qiime2.org/u/lizgehret)
#### Post date: [September 1, 2021, 9:17pm UTC](https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600/6 "2021-09-01T21:17:30Z")
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### Author:  [@system](https://forum.qiime2.org/u/system)
#### Post date: [October 3, 2021, 3:18am UTC](https://forum.qiime2.org/t/update-seppreferencetree-to-silva-138-1/20600/7 "2021-10-03T03:18:21Z")
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