A comparative genomics examination of desiccation tolerance and sensitivity in two sister grass species

第一作者：Ricardo A. Chávez Montes

第一单位：墨西哥生物多样性基因组学国家实验室

第一通讯：Melvin J. Oliver

 Abstarct 

背景回顾：Desiccation tolerance is an ancient and complex trait that spans all major lineages of life on earth. 

脱水耐受性是一种古老而复杂的性状，几乎地球上所有的生命谱系都具有这种性状。

提出问题：Although important in the evolution of land plants, the mechanisms that underlay this complex trait are poorly understood, especially for vegetative desiccation tolerance (VDT). 

尽管脱水耐受性在陆地植物的演化过程中非常重要，但人们对这种复杂性状的潜在分子机制知之甚少，尤其是对于植物耐脱水性（VDT）。

研究基础：The lack of suitable closely related plant models that offer a direct contrast between desiccation tolerance and sensitivity has hampered progress. We have assembled high-quality genomes for two closely related grasses, the desiccation-tolerant Sporobolus stapfianus and the desiccation-sensitive Sporobolus pyramidalis. Both species are complex polyploids; S. stapfianus is primarily tetraploid, and S. pyramidalis is primarily hexaploid. 

由于缺乏合适的近缘植物模型，即其中一个具有脱水耐受性，一个对脱水敏感，因此阻碍了对于植物脱水耐受性的深入研究。作者在先前的研究中组装了两个近缘的禾本科植物基因组，一个是耐脱水的复原草（Sporobolus stapfianus），另一个是对脱水敏感的大鼠尾草（Sporobolus pyramidalis）。这两个植物物种都是复杂的多倍体，复原草主要是四倍体，而大鼠尾草主要是六倍体。

结果1-姊妹种对脱水的转录响应差异：S. pyramidalis undergoes a major transcriptome remodeling event during initial exposure to dehydration, while S. stapfianus has a muted early response, with peak remodeling during the transition between 1.5 and 1.0 grams of water (gH₂O) g^-1 dry weight (dw). Functionally, the dehydration transcriptome of S. stapfianus is unrelated to that for S. pyramidalis.

大鼠尾草在遭遇脱水胁迫早期会经历一个转录重塑的过程，而复原草则在早期几乎保持沉默，而是在1.5 gH2O g-1 dw和1.0 gH2O g-1 dw脱水处理转变的时候出现重塑峰值。在功能上，复原草的脱水转录组与大鼠尾草的不一样。

结果2-耐脱水的转录准备：A comparative analysis of the transcriptomes of the hydrated controls for each species indicated that S. stapfianus is transcriptionally primed for desiccation. 

通过对两个物种进行吸水控制的比较转录组分析显示，复原草在转录层面上为脱水做好了准备。

结果3-耐脱水机制的不同起源：Cross-species comparative analyses indicated that VDT likely evolved from reprogramming of desiccation tolerance mechanisms that evolved in seeds and that the tolerance mechanism of S. stapfianus represents a recent evolution for VDT within the Chloridoideae.

跨物种比较分析表明，植物脱水耐受性可能是通过重编程种子的脱水耐受机制而演化过来的，而复原草的脱水耐受性则是虎尾草亚科内发生的一次最近的演化结果。

结果4-脱水响应：Orthogroup analyses of the significantly differentially abundant transcripts reconfirmed our present understanding of the response to dehydration, including the lack of an induction of senescence in resurrection angiosperms.

对于显著差异富集转录本的同源基因分析，进一步证实了我们对于脱水响应的理解，包括了复原被子植物中丢失了衰老诱导。

结论：The data also suggest that failure to maintain protein structure during dehydration is likely critical in rendering a plant desiccation sensitive.

本文的研究结果还表明，脱水过程中未能维持蛋白质结构可能是使植物对脱水敏感的关键。

doi: https://doi.org/10.1073/pnas.2118886119

Journal: PNAS

Published date: February 01, 2022