Center for Ecological Research, Kyoto University, Hirano, Otsu, Shiga, Japan.
Faculty of Education, Kagawa University, Saiwaicho, Takamatsu, Kagawa, Japan.
Ann Bot. 2018 Jun 8;121(7):1351-1360. doi: 10.1093/aob/mcy033.
An altitudinal gradient of leaf wettability is often observed between and within species. To understand its functional significance, positional variation of leaf surfaces within plants should be taken into account. In rosette-forming plants, rosette leaves are near the ground and their adaxial surfaces are exposed, whereas cauline leaves are lifted from the ground throughout the reproductive season, and their abaxial surfaces are more exposed. Here, we investigated leaf wettability of cauline and rosette leaves of Arabidopsis halleri subsp. gemmifera growing in contrasting montane habitats along an altitudinal gradient at Mt Ibuki, Japan.
We conducted field investigations and a growth chamber experiment to determine whether field-observed variation in leaf wettability was caused by genetic differentiation. We further performed gene expression analysis of a wax-related gene, i.e. AhgCER1, a homologue of A. thaliana ECERIFERUM1 (CER1) that may be involved in differentiation of leaf wettability.
We found cauline-leaf specific genetic differentiation in leaf wettability between contrasting montane habitats. Cauline leaves of semi-alpine plants, especially on abaxial surfaces, were non-wettable. Cauline leaves of low-altitudinal understorey plants were wettable, and rosette leaves were also wettable in both habitats. AhgCER1 expression corresponded to observed leaf wettability patterns.
Low wettability of cauline leaves is hypothesized to keep exposed surfaces dry when they are wrapping flowering buds in early spring, and presumably protects flowering buds from frost damage. The genetic system that controls wax content, specifically for cauline leaves, should be involved in the observed genetic differentiation, and AhgCER1 control is a strong candidate for the underlying genetic mechanism.
物种间和种内通常存在叶润湿性的海拔梯度。为了理解其功能意义，应考虑植物内叶片位置的变化。在莲座状形成的植物中，莲座叶靠近地面，其腹面暴露，而茎生叶在整个生殖季节都从地面升起，其背面更暴露。在这里，我们研究了在日本岩木山，沿海拔梯度的两个具有挑战性的山地生境中生长的拟南芥 Halleri 亚种。gemmifera 的茎生叶和莲座叶的叶润湿性。
我们进行了野外调查和生长室实验，以确定观察到的叶润湿性的变化是否是由遗传分化引起的。我们进一步分析了一个与蜡相关的基因 AhgCER1 的基因表达，即 A. thaliana ECERIFERUM1（CER1）的同源物，该基因可能参与了叶润湿性的分化。
我们发现，在具有挑战性的山地生境之间，莲座叶的叶润湿性存在茎生叶特有的遗传分化。半高山植物的茎生叶，特别是背面，不易润湿。低海拔林下植物的茎生叶是润湿的，在两个生境中莲座叶也是润湿的。AhgCER1 的表达与观察到的叶润湿性模式相对应。
推测茎生叶的低润湿性可以在早春包裹花芽时保持暴露表面干燥，并可能保护花芽免受霜害。控制蜡含量的遗传系统，特别是针对茎生叶，应该参与了观察到的遗传分化，而 AhgCER1 控制是潜在遗传机制的有力候选者。
