Goudet Myriam M M, Orr Douglas J, Melkonian Michael, Müller Karin H, Meyer Moritz T, Carmo-Silva Elizabete, Griffiths Howard
Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK.
Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
New Phytol. 2020 Aug;227(3):810-823. doi: 10.1111/nph.16577. Epub 2020 May 13.
Green algae expressing a carbon-concentrating mechanism (CCM) are usually associated with a Rubisco-containing micro-compartment, the pyrenoid. A link between the small subunit (SSU) of Rubisco and pyrenoid formation in Chlamydomonas reinhardtii has previously suggested that specific RbcS residues could explain pyrenoid occurrence in green algae. A phylogeny of RbcS was used to compare the protein sequence and CCM distribution across the green algae and positive selection in RbcS was estimated. For six streptophyte algae, Rubisco catalytic properties, affinity for CO uptake (K ), carbon isotope discrimination (δ C) and pyrenoid morphology were compared. The length of the βA-βB loop in RbcS provided a phylogenetic marker discriminating chlorophyte from streptophyte green algae. Rubisco kinetic properties in streptophyte algae have responded to the extent of inducible CCM activity, as indicated by changes in inorganic carbon uptake affinity, δ C and pyrenoid ultrastructure between high and low CO conditions for growth. We conclude that the Rubisco catalytic properties found in streptophyte algae have coevolved and reflect the strength of any CCM or degree of pyrenoid leakiness, and limitations to inorganic carbon in the aquatic habitat, whereas Rubisco in extant land plants reflects more recent selective pressures associated with improved diffusive supply of the terrestrial environment.
表达碳浓缩机制（CCM）的绿藻通常与一种含核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）的微区室——蛋白核相关联。莱茵衣藻中Rubisco小亚基（SSU）与蛋白核形成之间的联系此前表明，特定的RbcS残基可以解释绿藻中蛋白核的出现。利用RbcS的系统发育来比较绿藻中的蛋白质序列和CCM分布，并估计RbcS中的正选择。对六种链形植物藻类的Rubisco催化特性、对CO吸收的亲和力（K）、碳同位素分馏（δC）和蛋白核形态进行了比较。RbcS中βA-βB环的长度提供了一个区分绿藻纲和链形植物绿藻的系统发育标记。链形植物藻类中的Rubisco动力学特性已对诱导性CCM活性的程度作出响应，这表现为高CO₂和低CO₂生长条件下无机碳吸收亲和力、δC和蛋白核超微结构的变化。我们得出结论，链形植物藻类中发现的Rubisco催化特性是共同进化的，反映了任何CCM的强度或蛋白核渗漏程度，以及水生栖息地中无机碳的限制，而现存陆地植物中的Rubisco反映了与陆地环境中改善的扩散供应相关的最新选择压力。
