Highly variable chloroplast genome from two endangered Papaveraceae
lithophytes Corydalis tomentella and C. saxicola
Abstract
The increasingly wide application of chloroplast(cp) genome
super-barcode in taxonomy and the recent breakthrough in cp genetic
engineering make the development of new cp gene resources urgent and
significant. Corydalis is recognized as the most genotypes complicated
and taxonomically challenging plant taxa in Papaveraceae. However, no
complete cp genome for this genus has been reported to date. In this
study, we sequenced four complete cp genomes of two endangered
lithophytes Corydalis saxicola and C. tomentellav in Corydalis,
conducted a comparative genomics study on them, and a highly variable cp
genome structure was found. The cp genomes have a large genome size of
189,029 to 190,247 bp, possessing a quadripartite structure and with two
highly expanded inverted repeat (IR) regions (length: 41,955 to 42,350
bp). Comparison between the cp genomes of C. tomentella, C. saxicola and
Papaveraceae species, five NADH dehydrogenase-like genes (ndhF, ndhD,
ndhL, ndhG, ndhE) with psaC, rpl32, ccsA and trnL-UAG normally located
in the SSC region have migrated to IRs, resulting in IR expansion and
gene duplication. An up to 9 kb inversion involving five genes (rpl23,
ycf2, ycf15, trnI-CAU and trnL-CAA) was found within IR regions. The
accD gene was found to be absent and the ycf1 gene has shifted from the
IR/SSC border to the SSC region as a single copy. Phylogenetic analysis
based on the sequences of common CDS showed that the genus Corydalis is
quite distantly related to the other genera of Papaveraceae, it provided
a new clue for recent advocacy to establish a separate Fumariaceae
family. Our results revealed one special cp genome structure in
Papaveraceae, provided a useful resources for classification of the
genus Corydalis, and will be valuable for understanding Papaveraceae
evolutionary relationships.