Wolters Silva Melissa, Schwarz Lukas, Khairat Ronja, Sturm Kristina, Müller Boje, van Deenen Nicole, Twyman Richard M, Prüfer Dirk, Gronover Christian Schulze
Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Münster, Germany.
Institute of Plant Biology and Biotechnology, University of Münster, Münster, Germany.
Plant Cell Rep. 2025 Jun 24;44(7):155. doi: 10.1007/s00299-025-03537-3.
The presence of plastid-like structures in the latex of the Russian dandelion Taraxacum koksaghyz and interactions involving plastid-associated TkGGR1 with TkSRPP3, TkGGPS6 and TkLIL3 may confer TkSRPP-mediated stress tolerance. The latex of the Russian dandelion Taraxacum koksaghyz is a rich source of natural rubber (NR) but other facets of its metabolism and physiology have been largely neglected. Small rubber particle proteins (SRPPs) contribute to NR biosynthesis by stabilizing rubber particles and are also linked to stress responses. The identification of geranylgeranyl reductase (GGR1) as potential interactor of TkSRPP3 in our previous study prompted its detailed investigation because GGRs normally reduce geranylgeranyl groups to phytol or phytyl diphosphate for chlorophyll synthesis in chloroplasts. Here we determined the latex-specific expression and phytol-producing activity of GGR1, and confirmed its interaction with TkSRPP3. Metabolic analysis of plants with altered TkGGR1 expression levels in latex revealed its involvement in tocopherol but not NR synthesis in roots, whereas a second, leaf-specific GGR was responsible for chlorophyll synthesis. We found that a geranylgeranyl diphosphate synthase (GGPS) and light-harvesting-like 3 protein (LIL3) were co-expressed in latex and translocated into Nicotiana benthamiana chloroplasts, as we also observed for TkGGR1. We confirmed that TkGGR1 interacted with TkGGPS6 and TkLIL3 inside chloroplasts and detected an extraplastidial interaction between TkLIL3 and TkSRPP4. In situ analysis of mVenus-tagged TkGGR1 indicated its localization in plastid-like structures in T. koksaghyz latex, which lacks conventional chloroplasts. We therefore hypothesized the presence of a TkGGR1-containing multiprotein complex within Frey-Wyssling-like particles in latex that may confer oxidative stress tolerance. This study provides insight into a previously undescribed branch of isoprenoid metabolism and cellular biology of NR-producing laticifers in T. koksaghyz.
俄罗斯蒲公英（Taraxacum koksaghyz）乳汁中质体样结构的存在，以及质体相关的TkGGR1与TkSRPP3、TkGGPS6和TkLIL3之间的相互作用，可能赋予TkSRPP介导的胁迫耐受性。俄罗斯蒲公英（Taraxacum koksaghyz）的乳汁是天然橡胶（NR）的丰富来源，但其代谢和生理的其他方面在很大程度上被忽视了。小橡胶粒子蛋白（SRPPs）通过稳定橡胶粒子促进天然橡胶的生物合成，并且也与胁迫反应有关。在我们之前的研究中，香叶基香叶基还原酶（GGR1）被鉴定为TkSRPP3的潜在相互作用因子，这促使对其进行详细研究，因为GGRs通常将香叶基香叶基基团还原为叶绿醇或植基二磷酸用于叶绿体中的叶绿素合成。在这里，我们确定了GGR1在乳汁中的特异性表达和产生叶绿醇的活性，并证实了它与TkSRPP3的相互作用。对乳汁中TkGGR1表达水平改变的植物进行代谢分析，结果显示它参与根中生育酚的合成，但不参与天然橡胶的合成，而另一种叶特异性的GGR负责叶绿素的合成。我们发现，香叶基香叶基二磷酸合酶（GGPS）和类捕光3蛋白（LIL3）在乳汁中共同表达，并转运到本氏烟草叶绿体中，就像我们对TkGGR1所观察到的那样。我们证实，TkGGR1在叶绿体内与TkGGPS6和TkLIL3相互作用，并检测到TkLIL3与TkSRPP4之间的质体外相互作用。对mVenus标记的TkGGR1进行原位分析，结果表明它定位于俄罗斯蒲公英乳汁中缺乏传统叶绿体的质体样结构中。因此，我们推测在乳汁中类Frey-Wyssling颗粒内存在一种含TkGGR1的多蛋白复合物，它可能赋予氧化胁迫耐受性。这项研究为俄罗斯蒲公英中天然橡胶生产乳管细胞类异戊二烯代谢和细胞生物学一个以前未描述的分支提供了见解。
