Not all lipids in xylem conduits are artefacts. A reply to Yamagishi et al.
Not all lipids in xylem conduits are artefacts. A reply to Yamagishi et al.
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并非木质部导管中的所有脂质都是人工制品。
DOI：
10.1163/22941932-00002186
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发表时间：
2021
期刊：
影响因子：
1.9
通讯作者：
Schenk, H. Jochen
中科院分区：
文献类型：
--
作者：
Jansen, Steven;Schenk, H. Jochen
Yamagishi等人的论文。（2021）代表了对被子植物木材中导管间纹孔膜上结壳的分布和形成的有趣研究，这在许多物种中都有报道。作者提出了明确和令人信服的证据表明，结壳或涂层坑膜代表中性脂质，如三酰甘油，并形成在脱水过程中的木材样品作为一个人工制品的干燥或可能作为一个过程，也可能发生在非功能管道的活植物。我们很高兴地看到，作者详细研究了木质部导管中的脂质，并应用了飞行时间二次离子质谱等新方法。我们也希望这些作者或其他研究小组在未来的工作中跟进这些发现。正如论文中所提到的，干燥样品中的纹孔膜结壳（PMI）中的脂质不能与水合二甲苯样品中的两亲性脂质相比。然而，作者做了一些错误和不幸的陈述，很容易被读者误解，这可能导致混乱和错误的信息。我们的主要评论是，必须明确区分所研究的中性脂质和极性两亲性脂质，例如半乳糖脂和磷脂，它们在大多数物种的木质部中比中性脂质更丰富（脂肪储存物种除外）（Schenk等人，2021）。不幸的是，论文的标题和摘要没有明确指出只研究了中性脂质，这可能会给那些没有阅读摘要以外内容的读者造成一种错误的印象，即这些发现也适用于木质部导管中的极性脂质。基于仔细的质谱分析和基于共聚焦显微镜的视觉证据，有强有力的证据表明，水合样品木质部导管中的大多数脂质是极性脂质（Schenk等人，2017、2018、2021）。我们很清楚，早期对木质部汁液化学的研究可能受到活细胞（薄壁组织或活纤维）的木质部汁液污染（Schurr 1998）。因此，在从茎中提取木质部汁液时，研究污染控制样品至关重要，例如将1 ml纯水暴露于高压清洁的切开茎表面1分钟，以及测试茎另一端切割细胞的潜在污染（Schenk等人，2017，2021）。
The paper by Yamagishi et al.(2021) represents an interesting study on the distribution and formation of incrustations on intervessel pit membranes in angiosperm wood, which have been reported in a wide range of species. The authors present clear and convincing evidence that the incrustations or coatings on pit membranes represent neutral lipids such as triacylglycerols, and are formed during dehydration of wood samples either as an artifact of drying or possibly as a process that could also occur in non-functional conduits of living plants. We are excited to see that lipids in xylem conduits were examined in detail by the authors and that novel methods such as time-of-flight secondary ion mass spectrometry were applied. We also hope that these authors or other research groups will follow up on the findings in future work. As mentioned in the paper, lipids of pit membrane incrustations (PMIs) in dried samples cannot be compared to amphiphiliclipidsfoundinhydratedxylemsamples. However, theauthorsmadeafewomissionsandunfortunatestatements that could easily be misinterpreted by readers, which could lead to confusion and misinformation. Our major comment is that a clear distinction must be made between the neutral lipids studied, and polar, amphiphilic lipids such as galactolipids and phospholipids, which are more abundant in xylem of most species than neutral lipids (with the exception of fat-storing species)(Schenk et al. 2021). Unfortunately, the title and abstract of the paper do not specify that only neutral lipids were studied, which could create a false impression for readers who do not read beyond the abstract that the findings apply to polar lipids in xylem conduits as well.There is strong and solid evidence based on careful mass spectrometry analyses and visual evidence based on confocal microscopy that most of the lipids in xylem conduits of hydrated samples are polar lipids (Schenk et al. 2017, 2018, 2021). We are well aware that earlier studies on xylem sap chemistry may have suffered from xylem sap contamination by livings cells (parenchyma or living fibres)(Schurr 1998). For this reason, it is essential in xylem sap extractions from stems to investigate contamination control samples, such as 1 ml of pure water exposed to a high-pressure-cleaned cut open stem surface for 1 minute as well as testing for potential contamination from cut cells at the other end of a stem (Schenk et al. 2017, 2021).