Amaranthaceae (incl. Chenopodiaceae) show an immense diversity of C₄ syndromes. More than 15 independent origins of C₄ photosynthesis, partly in halophytic and/or succulent lineages, and the largest number of C₄ species in eudicots signify the importance of this angiosperm lineage in C₄ evolution. Here, we conduct RNA-Seq followed by comparative transcriptome analysis of three species from Camphorosmeae representing related clades with different photosynthetic types: Threlkeldia diffusa (C₃), Sedobassia sedoides (C₂), and Bassia prostrata (C₄). Results show that B. prostrata belongs to the NADP-ME type and core genes encoding for C₄ cycle are significantly up-regulated when compared to Sed. sedoides and T. diffusa, Sedobassia sedoides and B. prostrata share a number of up-regulated C₄-related genes, however, two C₄ transporters (DIT and TPT) are found significantly up-regulated only in Sed. sedoides. Combined analysis of transcription factors (TFs) of the closely related lineages (Camphorosmeae and Salsoleae) revealed that no C₃ specific TFs is higher in C₂ species as compared to C₄ species, instead the C₂ species show their own set of up-regulated TFs. Taken together, our study indicates that the hypothesis of the C₂ photosynthesis as a proxy towards C₄ photosynthesis is questionable in Sed. sedoides and more in favour of an independent evolutionary stable-state.

中文翻译：

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使用RNA-Seq深入了解苋科/藜科C2和C4光合作用的调控

苋科（包括藜科）显示出 C ₄综合征的巨大多样性。超过 15 个独立的 C ₄光合作用起源，部分位于盐生植物和/或多肉植物谱系，以及真双子叶植物中最多的 C ₄物种，表明这种被子植物谱系在 C ₄进化中的重要性。在这里，我们进行RNA测序，然后从三个物种比较转录组分析Camphorosmeae表示具有不同光合类型相关的分支：Threlkeldia白花蛇舌草（C ₃），Sedobassia sedoides（C ₂），和木地肤（C₄）。结果表明，与Sed相比，B. prostrata属于 NADP-ME 类型，编码 C ₄循环的核心基因显着上调。sedoides和T. diffusa、Sedobassia sedoides和B. prostrata共享许多上调的 C ₄相关基因，然而，发现两个 C ₄转运蛋白（DIT 和 TPT）仅在Sed 中显着上调。sedoides。密切相关的谱系（转录因子（TF）的组合分析Camphorosmeae和Salsoleae）显示无C ₃特定TFS是在C时₂与 C ₄物种相比，C ₂物种显示出它们自己的一组上调的 TF。总之，我们的研究表明 C ₂光合作用作为 C ₄光合作用代理的假设在Sed 中是有问题的。sedoides 等，更倾向于独立的进化稳定状态。