Plastid Genome Evolution by Shu-Miaw Chaw Robert K. Jansen & Robert K. Jansen

Author:Shu-Miaw Chaw,Robert K. Jansen & Robert K. Jansen
Language: eng
Format: epub
ISBN: 9780128134580
Publisher: Elsevier Ltd.
Published: 2018-01-23T16:00:00+00:00

4.5 Introns and Their Encoded Proteins

Chlorophyte plastomes contain a plethora of introns. The 643 group I introns and 442 group II introns identified in the plastomes examined in this review represent 92 and 143 distinct sites of insertion, respectively (Fig. 4). With the exception of two group II introns of the ulotrichalean G. planctonica (Turmel, Otis, et al., 2016), they are all located within coding regions of canonical genes. Nearly half of the canonical genes (66/141) are interrupted by introns, and while group II introns occur in most of these genes (63/66), group I introns are restricted to 18 genes (Fig. 5A). Genes encoding components of photosystems I and II are the most intron rich, with 28 insertion sites identified in psbA alone. The rRNA genes also contain introns at many sites, but these are exclusively of the group I family. While all chlorophyte group I introns are cis-spliced, trans-spliced group II introns occur in five genes of the Chlorophyceae—psaA (de Cambiaire et al., 2006; Fucikova, Lewis, & Lewis, 2016; Goldschmidt-Clermont et al., 1991) and rpl32 (see GenBank accessions listed in Lemieux, Vincent, Labarre, Otis, & Turmel, 2015) in the Chlamydomonadales and Sphaeropleales, and petD, psaC, and rbcL in the OCC clade (Bélanger et al., 2006; Brouard et al., 2010)—as well as in the ycf3 gene of the clade-VIIC prasinophyte Picocystis salinarum (Lemieux et al., 2014b).

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