Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, Hadassah Medical School, The Hebrew University of Jerusalem, Jerusalem, 91120, Israel.
Plant J. 2021 Jun;106(6):1746-1758. doi: 10.1111/tpj.15269. Epub 2021 Apr 30.
Floral guides are patterned cues that direct the pollinator to the plant reproductive organs. The spatial distribution of showy visual and olfactory traits allows efficient plant-pollinator interactions. Data on the mechanisms underlying floral volatile patterns or their interactions with pollinators are lacking. Here we characterize the spatial emission patterns of volatiles from the corolla of the model plant Petunia × hybrida and reveal the ability of honeybees to distinguish these patterns. Along the adaxial epidermis, in correlation with cell density, the petal base adjacent to reproductive organs emitted significantly higher levels of volatiles than the distal petal rim. Volatile emission could also be differentiated between the two epidermal surfaces: emission from the adaxial side was significantly higher than that from the abaxial side. Similar emission patterns were also observed in other petunias, Dianthus caryophyllus (carnation) and Argyranthemum frutescens (Marguerite daisy). Analyses of transcripts involved in volatile production/emission revealed lower levels of the plasma-membrane transporter ABCG1 in the abaxial versus adaxial epidermis. Transient overexpression of ABCG1 enhanced emission from the abaxial epidermis to the level of the adaxial epidermis, suggesting its involvement in spatial emission patterns in the epidermal layers. Proboscis extension response experiments showed that differences in emission levels along the adaxial epidermis, that is, petal base versus rim, detected by GC-MS are also discernible by honeybees.
花部引导结构是一种模式线索，它可以引导传粉者到达植物的生殖器官。艳丽的视觉和嗅觉特征的空间分布允许植物与传粉者进行有效的相互作用。目前缺乏有关花部挥发物模式的形成机制或其与传粉者相互作用的相关数据。在这里，我们描述了模式植物矮牵牛花冠挥发物的空间释放模式，并揭示了蜜蜂区分这些模式的能力。沿近轴表皮，与细胞密度相关，靠近生殖器官的花瓣基部比远轴花瓣边缘释放出显著更高水平的挥发物。也可以区分两个表皮表面的挥发物释放：近轴侧的释放明显高于远轴侧。在其他矮牵牛、香石竹（康乃馨）和非洲菊（玛格丽特雏菊）中也观察到了类似的释放模式。参与挥发物产生/释放的转录本分析显示，质膜转运蛋白 ABCG1 在远轴表皮中的水平低于近轴表皮。ABCG1 的瞬时过表达增强了远轴表皮的挥发物释放，使其达到近轴表皮的水平，这表明其参与了表皮层的空间释放模式。触须延伸反应实验表明，GC-MS 检测到的沿近轴表皮（即花瓣基部与边缘）的挥发物释放水平的差异，也可以被蜜蜂识别。
