The genome of the recretohalophyte Limonium bicolor provides insights into salt gland development and salinity adaptation during terrestrial evolution

第一作者：Fang Yuan

第一单位：山东师范大学

通讯作者：Bao-Shan Wang

 Abstarct 

背景回顾：Halophytes have evolved specialized strategies to cope with high salinity. The extreme halophyte sea lavender (Limonium bicolor) lacks trichomes but possesses salt glands on its epidermis, which can excrete harmful ions such as sodium to avoid salt damage. 

盐生植物已经演化出了特化的策略，以应对生长环境中的高盐胁迫。极端盐生植物二色补血草（Limonium bicolor）缺少表皮腺毛，但是其在表皮上存在盐腺，可以分泌钠等有害离子，从而避免盐损伤。

主要研究：Here, we report a high-quality, 2.92-Gb chromosome-scale L. bicolor genome assembly using a combination of Illumina short reads, single-molecule real-time long reads, chromosome conformation capture (Hi-C) data, and Bionano genome maps, which have greatly enriched genomic information of recretohalophyte with multicellular salt glands. 

本文中，作者通过整合Illumina短读长、SMRT长读长、HiC测序以及Bionano图谱数据，报道了二色补血草2.92Gb的染色体层级基因组组装，极大地丰富了带有多细胞盐腺的泌盐盐生植物的基因组信息。

结果1-无腺毛的分子解释：Although the L. bicolor genome possesses genes showing similarity to trichome fate genes from Arabidopsis (Arabidopsis thaliana), it lacks homologs of the decision fate genes GLABRA3, ENHANCER OF GLABRA3, GLABRA2, TRANSPARENT TESTA GLABRA2, and SIAMESE, providing a molecular explanation for the absence of trichomes in this species. 

尽管二色补血草的基因组中含有与拟南芥中腺毛命运基因相似的基因，但是二色补血草缺少命运决定基因GLABRA3、ENHANCER OF GLABRA3、GLABRA2、TRANSPARENT TESTA GLABRA2以及SIAMESE的同源基因，这为该物种中缺少腺毛提供了分子层面的解释。

结果2-盐腺关键基因：We identified key genes (LbHLH and LbTTG1) controlling salt gland development among classical trichome homologous genes and confirmed their roles by showing that their mutation markedly disrupted salt gland initiation, salt secretion and salt tolerance, thus offering the genetic support for the long-standing hypothesis that salt glands and trichomes may share a common origin.

作者从典型的腺毛同源基因中鉴定到了控制盐腺发育的关键基因LbHLH和LbTTG1，并通过突变后出现盐腺起始、盐外泌以及盐耐受性被明显扰乱等表型进一步确认了这关键基因的功能，从而为盐腺与腺毛可能有共同的起源这一长期存在的假说提供了实质的遗传学证据。

结果3-WGD：In addition, a whole-genome duplication event occurred in the L. bicolor genome after its divergence from Tartary buckwheat, which may have contributed to its adaptation to high salinity.

另外，在二色补血草基因组中检测到一次在其与苦荞分化后发生的全基因组复制事件，可能促进了该物种的高盐适应性演化。

结论：The L. bicolor genome resource gives profound insights into plant salt tolerance mechanisms that should facilitate the engineering of salt-tolerant crops.

二色补血草基因组资源为植物的耐盐机制研究提供了意义深远的见解，有助于加速耐盐作物新品种的开发。

** 王宝山 **

doi: https://doi.org/10.1016/j.molp.2022.04.011

Journal: Molecular Plant

First Published: May 04, 2022