Patterns of Nucleotide Diversity of the ldpA Circadian Gene in Closely Related Species of Cyanobacteria from Extreme Cold Deserts

Abstract

In the circadian system of cyanobacteria, the ldpA gene is a component of the input to the clock. We comparatively analyzed nucleotide polymorphism of this gene in populations of two closely related species of cyanobacteria (denoted as Synechococcus species S1 and S2, respectively) from extreme cold deserts in Antarctica, the Canadian Arctic, and Tibet. Although both species manifested similarly high haplotype diversities (0.990 and 0.809, respectively), the nucleotide diversity differed significantly (0.0091 in S1 and 0.0037 in S2). The populations of species S2 were more differentiated (F ST ‫؍‬ 0.2242) compared to those of species S1 (F ST between 0.0296 and 0.1188). An analysis of positive selection with several tests yielded highly significant values (P < 0.01) for both species. On the other hand, these results may be somewhat compromised by fluctuating population sizes of the species. The apparent selection pressure coupled with the pronounced demographic factors, such as population expansion, small effective population size, and genetic drift, may thus result in the observed significant interpopulation differentiation and subsequent speciation of cyanobacteria.

Diverse metabolic and stress-tolerance pathways in chasmoendolithic and soil communities of Miers Valley, McMurdo Dry Valleys, Antarctica

“…It is not clear how cyanobacterial nitrogen fixation may be regulated under a 24-hr daylight scenario during the austral summer, since it is usually a dark reaction inhibited by oxygenic photosynthesis (Fay 1992). Circadian controls on primary metabolism may emerge as important in this regard (Ng et al 2013). Overall these findings support the notion of a continuous soil-rock surface community (SRSC) forming a 'blanket' of surface biological activity in arid landscapes (Pointing and Belnap 2012), and these cryptogamic covers are likely globally important sources of carbon and nitrogen fixation (Elbert et al 2012).…”

Phylogeography indicates incomplete genetic divergence among phenotypically differentiated montane forest populations of Atlapetes albinucha (Aves, Passerellidae)

“…For most of these cases, present distribution of the genetic diversity may reflect the retention of the genetic diversity found in the ancestor for a long time after isolation, which may have had a larger population size, thus increasing the time for some polymorphisms to be retained (Joseph and Omland 2009). Similarly, population expansion derived from populations with high effective sizes may also explain the haplotype and nucleotide diversities observed (Harpending et al 1998, Ray et al 2003, Ng et al 2013, Jezkova et al 2015).…”

Evolution of the circadian clock system in cyanobacteria: a genomic perspective

“…Хотя в некоторые периоды эволюции циркадных генов происходил эпизодический положительный отбор, главную роль сыграл отрицательный отбор Dvornyk, 2005). Однако положительный отбор является более выраженным на уровне популяции (Dvornyk et al, 2003;Dvornyk, Jahan, 2012;Ng et al, 2013). На состав циркадной системы различных таксонов цианобактерий влияло не только вовлечение новых генов, но и потеря некоторых из них (например, kaiA и cikA) (Baca et al, 2010).…”