Laboratório de Fisiologia Molecular de Plantas, Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Núcleo de Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, PR, Brazil.
Planta. 2022 Feb 3;255(3):57. doi: 10.1007/s00425-022-03841-2.
The plastome of Melocactus glaucescens shows unique rearrangements, IR expansion, and unprecedented gene losses in Cactaceae. Our data indicate tRNA import from the cytosol to the plastids in this species. Cactaceae represents one of the richest families in keystone species of arid and semiarid biomes. This family shows various specific features comprehending morphology, anatomy, and metabolism, which allow them to grow under unfavorable environmental conditions. The subfamily Cactoideae contains the most divergence of species, which are highly variable in growth habit and morphology. This subfamily includes the endangered species Melocactus glaucescens (tribe Cereeae), which is a cactus endemic to the biome Caatinga in Brazil. Aiming to analyze the plastid evolution and develop molecular markers, we sequenced and analyzed in detail the plastome of M. glaucescens. Our analyses revealed that the M. glaucescens plastome is the most divergent among the species of the family Cactaceae sequenced so far. We characterized here unique rearrangements, expanded IRs containing an unusual set of genes, and several gene losses. Some genes related to the ndh complex were lost during the plastome evolution, while others have lost their functionality. Additionally, the loss of three tRNA genes (trnA-UGC, trnV-UAC, and trnV-GAC) suggests tRNA import from the cytosol to the plastids in M. glaucescens. Moreover, we identified high gene divergence, several putative positive signatures, and possible unique RNA-editing sites. Furthermore, we mapped 169 SSRs in the plastome of M. glaucescens, which are helpful to access the genetic diversity of natural populations and conservation strategies. Finally, our data provide new insights into the evolution of plastids in Cactaceae, which is an outstanding lineage adapted to extreme environmental conditions and a notorious example of the atypical evolution of plastomes.
Melocactus glaucescens 的质体基因组显示出独特的重排、IR 扩张和在仙人掌科中前所未有的基因丢失。我们的数据表明，在该物种中，tRNA 从细胞质输入到质体。仙人掌科是干旱和半干旱生物群落中关键物种最丰富的科之一。该科表现出各种独特的特征，包括形态、解剖和代谢，这使它们能够在不利的环境条件下生长。仙人掌亚科包含最多的物种分化，这些物种在生长习性和形态上高度多样化。该亚科包括濒临灭绝的物种 Melocactus glaucescens（Cereeae 部落），这是一种原产于巴西 Caatinga 生物群落的仙人掌。为了分析质体进化并开发分子标记，我们对 M. glaucescens 的质体进行了测序和详细分析。我们的分析表明，M. glaucescens 的质体是迄今为止测序的仙人掌科物种中最具分化的。我们在这里描述了独特的重排、包含一组不寻常基因的扩展 IR 以及几个基因丢失。在质体进化过程中，一些与 ndh 复合物相关的基因丢失，而其他基因则失去了功能。此外，三个 tRNA 基因（trnA-UGC、trnV-UAC 和 trnV-GAC）的丢失表明 M. glaucescens 中的 tRNA 从细胞质输入到质体。此外，我们鉴定了高基因分化、几个可能的正选择信号和可能独特的 RNA 编辑位点。此外，我们在 M. glaucescens 的质体中映射了 169 个 SSRs，这有助于评估自然种群的遗传多样性和保护策略。最后，我们的数据为仙人掌科质体进化提供了新的见解，这是一个适应极端环境条件的杰出谱系，也是质体非典型进化的一个显著例子。
