Institute of Biology, Laboratory of Evolutive Entomology, University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland.
Department of Functional and Evolutionary Entomology, Gembloux Agro-Bio Tech, University of Liege, Passage des Déportés 2, 5030, Liege, Belgium.
Planta. 2019 Oct;250(4):1281-1292. doi: 10.1007/s00425-019-03221-3. Epub 2019 Jun 25.
Cyanogenic glycosides present in the seeds of wild lima bean plants are associated with seedling defense but do not affect seed germination and seedling growth. Wild lima bean plants contain cyanogenic glycosides (CNGs) that are known to defend the plant against leaf herbivores. However, seed feeders appear to be unaffected despite the high levels of CNGs in the seeds. We investigated a possible role of CNGs in seeds as nitrogen storage compounds that influence plant growth, as well as seedling resistance to herbivores. Using seeds from four different wild lima bean natural populations that are known to vary in CNG levels, we tested two non-mutually exclusive hypotheses: (1) seeds with higher levels of CNGs produce seedlings that are more resistant against generalist herbivores and, (2) seeds with higher levels of CNGs germinate faster and produce plants that exhibit better growth. Levels of CNGs in the seeds were negatively correlated with germination rates and not correlated with seedling growth. However, levels of CNGs increased significantly soon after germination and seeds with the highest CNG levels produced seedlings with higher CNG levels in cotyledons. Moreover, the growth rate of the generalist herbivore Spodoptera littoralis was lower in cotyledons with high-CNG levels. We conclude that CNGs in lima bean seeds do not play a role in seed germination and seedling growth, but are associated with seedling defense. Our results provide insight into the potential dual function of plant secondary metabolites as defense compounds and storage molecules for growth and development.
野利马豆植物种子中的氰苷与幼苗防御有关，但不影响种子萌发和幼苗生长。野利马豆植物含有氰苷（CNGs），已知这些氰苷可以抵御植物的叶片食草动物。然而，尽管种子中的 CNG 含量很高，但种子取食者似乎并未受到影响。我们研究了 CNG 在种子中作为氮储存化合物的可能作用，这些化合物会影响植物的生长以及幼苗对食草动物的抗性。我们使用来自四个不同野利马豆自然种群的种子，这些种群已知在 CNG 水平上存在差异，我们检验了两个非互斥的假设：（1）CNG 水平较高的种子会产生对一般食草动物更具抗性的幼苗，以及（2）CNG 水平较高的种子萌发更快，产生的植物生长更好。种子中的 CNG 水平与萌发率呈负相关，与幼苗生长无关。然而，种子萌发后 CNG 水平会显著升高，并且 CNG 水平最高的种子会在子叶中产生 CNG 水平更高的幼苗。此外，食草动物斜纹夜蛾在 CNG 水平高的子叶中的生长速度较低。我们得出的结论是，野利马豆种子中的 CNG 不会影响种子萌发和幼苗生长，但与幼苗防御有关。我们的研究结果为植物次生代谢物作为防御化合物和生长发育的储存分子的潜在双重功能提供了新的见解。
