DOI: https://doi.org/10.21203/rs.3.rs-322257/v1
Objective
Secale sylvestre is a wild species of rye, morphologically distinct from domestic species. To draw comparisons between species based on molecular features, it is important to have high quality sequences, especially in the case of organellar genomes. For such reason, the complete chloroplast genome of Secale sylvestre Host introd. no. 6047 will provide useful data for ecological, agricultural and phylogenetic purposes.
Results
Here we present the complete, annotated chloroplast genome sequence of Secale sylvestre Host introd. no. 6047. The genome is 137116 bp long. The genome can be accessed on GenBank with the accession number (MW557517).
Secale is a small but very diverse genus from the tribe Triticeae (family Poaceae). It includes annual, perennial, self-pollinating and open-pollinating, cultivated, weedy and wild species of various morphologies. The genus Secale includes for now four species whose phylogenetic relationships have not been fully determined (GRIN, http://www.arsgrin.gov). This causes a significantly reduction of progress in rye breeding that can be enriched with functional traits derived from wild rye species. In the genus, the wild species Secale sylvestre Host (1809) is singularized by several genetic peculiarities [1, 2, 3, 4, 5]
Among the 8 chloroplast genome of Secale spp. available on GenBank, none is complete strictly speaking, with the second copy of the IR missing all the time, and with the exception of Secale cereale KC912691, they all display several ambiguous and non-attributed bases, rending it difficult to perform accurate SNPs comparisons. Thus, we presume that analysis of the complete chloroplast genome sequences of Secale spp., starting with S. sylvestre, will be useful and cost-effective for evolutionary and phylogenetic studies, as it was suggested by our previous studies [6, 7].
Seeds of Secale sylvestre Host introd. no. 6047 were obtained from the Botanical Garden of the Polish Academy of Sciences in Warsaw. Total DNA was extracted from young sprouts following Doyle and Doyle [8]. Sequencing took place in BGI Shenzhen’s facilities on a DNBSEQ platform. An amount of ca. 40 million clean 100 bp paired-end reads was obtained, and assembled using SPAdes 3.14.0 [9] with a k-mer of 85. The contigs corresponding to the chloroplast genome were joined together using Consed [10]. Annotations were performed with the help of GeSeq [11] and manually curated.
The genome is 137116 bp long (Table 1). The LSC is 81132 bp long, the SSC is 12820 bp long and the IR is 21582 bp long. No ambiguous bases were found in the genome.
As stated above, SNP calling type of analysis were rendered difficult by the presence among 7 out of 8 of the other available genomes of numerous non-attributed bases. Instead, analyzes focused on the presence of indels. To do so, chloroplast genomes were partitionned by sub-units, aligned using MAFFT 7 [12] and then vizualized using MEGAX [13].
Results provided evidences of the strong proximity between S. sylvestre Host introd. no. 6047 and Secale strictum voucher R 1108 (KY636137). A total of 16 indels were found to be common between these two strains, that discriminate them from all other (KC912691, KY636135, KY636136, KY636132, KY636134, KY636133, KY636138). The size of these indels ranges from 2 to 36 bp. Among these indels, 13 of were found in intergenic sequences (rpl32 – tRNA-L; psaC – ndhE; rrn16 – trnI-GAU; atpH – atpF; psaA – ycf3; trnT-UGU – trnL-UAA; trnF-GAA – ndhJ; atpB – rbcL; ycf4 – cemA; trnP-UGG – psaJ; psaJ – rpl33; clpP – psbB; rpl16 – rps3). It is worth being underlined that the last three indels occurred in intronic sequences, one inside a tRNA (intron trnK-UUU), two inside protein-coding genes (intron rps16; intron petD), a feature that received recent attention [14, 15], especially for the purpose of genetic distinction between closely related species [16].
Limitations
The protocol itself showed no limitation, as it allowed to obtain complete and non-ambiguous genome sequence. However, far more clean genome sequences are needed in order to describe the most reliable molecular markers for species identification and phylogeny, especially for what concerns SNPs.
LSC: large single copy; SSC: short single copy; IR: inverted repeat; bp: base pair.
Acknowledgements
Not applicable.
Authors’ contributions
LS, RG and AS conducted experiments and drafted the manuscript. Bioinformatic analyses were performed by RG.
Funding
RG thanks the Horizon 2020 Research and Innovation Programme GHaNA (The Genus Haslea, New marine resources for blue biotechnology and Aquaculture) under Grant Agreement No 734708/GHANA/ H2020-MSCA-RISE-2016, and the 2017-2021 research funds granted for the implementation of a co-financed international research project from Polish Ministry of Science and Higher Education.
Availability of data materials
The genome has been deposited on GenBank with the accession number MW557517. It is also available on Zenodo with the following link: http://doi.org/10.5281/zenodo.4537281
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interest.
Table 1 Overview of the data files/data sets.
|
Label |
File types (file extension) |
Data repository and identifier (DOI or accession number) |
|
Secale sylvestre chloroplast, complete genome |
FASTA, annotated GBK |
MW557517 |