The chloroplast genome of the desiccation-tolerant moss Pseudocrossidium replicatum (Taylor) R.H. Zander

Abstract

Mosses in conjunction with hornworts and liverworts are collectively referred to as bryophytes. These seedless, nonvascular plants are the closest extant relatives of early terrestrial plants and their study is essential to understand the evolutionary first steps of land plants. Here we report the complete chloroplast (cp) genome sequence of Pseudocrossidium replicatum, a moss belonging to the Pottiaceae family that is common in the central highlands of Mexico, in South America, in southern USA, and in Kenia. The cp genome (plastome) of P. replicatum is 123,512 bp in size, comprising inverted repeats of 9,886 bp and single-copy regions of 85,146 bp (LSC) and 18,594 bp (SSC). The plastome encodes 82 different proteins, 31 different tRNAs, and 4 different rRNAs. Phylogenetic analysis using 16 cp protein-coding genes demonstrated that P. replicatum is closely related to Syntrichia ruralis, and the most basal mosses are Takakia lepidozioides followed by Sphagnum palustre. Our analysis indicates that during the evolution of the mosses' plastome, eight genes were lost. The complete plastome sequence reported here can be useful in evolutionary and population genetics.

Figure 1. Gene map of the moss P. replicatum. Genes in the inside of the map are transcribed clockwise, and genes in the outside of the map are transcribed counterclockwise. Exons are indicated as closed boxes. Genes with related function are shown in the same color.

Figure 2. Phylogenetic tree of chloroplast genomes of mosses. A Neighbor joining tree was constructed using a concatenated alignment of 16 proteins: accD, atpA, atpB, cemA, chlB, chlL, clpP, ndhB, ndhF, ndhH, ndhK, petA, psaA, psbC, rbcL, andrps2. The chloroplast sequence of the fern Osmundastrum cinnamomeum was used as outgroup. Asterisks indicate boot-strap values > 85%. Arrows indicate gene insertion (down) or deletion (up). The scale represents number of amino acid substitution per site.

Figure 3. Comparison of chloroplast genome structure between mosses. Shown are the genome distances and gene position in the vicinity of LSC, IRB, SSC, and IRA in the genome structure of mosses cp.