Roles of BdUNICULME4 and BdLAXATUM‐A in the non‐domesticated grass Brachypodium distachyon

In cultivated grasses, tillering, spike architecture and seed shattering represent major agronomical traits. In barley, maize and rice, the NOOT‐BOP‐COCH‐LIKE (NBCL) genes play important roles in development, especially in ligule development, tillering and flower identity. However, compared with dicots, the role of grass NBCL genes is underinvestigated. To better understand the role of grass NBCLs and to overcome any effects of domestication that might conceal their original functions, we studied TILLING nbcl mutants in the non‐domesticated grass Brachypodium distachyon. In B. distachyon, the NBCL genes BdUNICULME4 (CUL4) and BdLAXATUM‐A (LAXA) are orthologous, respectively, to the barley HvUniculme4 and HvLaxatum‐a, to the maize Zmtassels replace upper ears1 and Zmtassels replace upper ears2 and to the rice OsBLADE‐ON‐PETIOLE1 and OsBLADE‐ON‐PETIOLE2/3. In B. distachyon, our reverse genetics study shows that CUL4 is not essential for the establishment of the blade–sheath boundary but is necessary for the development of the ligule and auricles. We report that CUL4 also exerts a positive role in tillering and a negative role in spikelet meristem activity. On the other hand, we demonstrate that LAXA plays a negative role in tillering, positively participates in spikelet development and contributes to the control of floral organ number and identity. In this work, we functionally characterized two new NBCL genes in a context of non‐domesticated grass and highlighted original roles for grass NBCL genes that are related to important agronomical traits.     

蒙农红豆草不同花色表型及色素成分特征分析

蒙农红豆草不仅是良好的饲草作物,还可以用作庭院观赏及蜜源植物。该研究以蒙农红豆草浅色花瓣突变体与对照群体中的粉红色、紫红色花瓣为试验材料,通过对花瓣颜色的表型和色素种类及含量的综合分析,明确影响花色形成的主要物质。结果表明:(1)蒙农红豆草浅色花突变体与对照的粉红色花和紫红色花为3种不同的色系,根据黄度(b*)和色相角(h°)将浅色花突变体的花色定义为黄白色花。(2)在3种花色中共检测到10种类黄酮和5种花青素,其中6种山奈酚衍生物、2种矮牵牛素衍生物、2种飞燕草素衍生物和1种锦葵素衍生物为首次在蒙农红豆草中报道;同时还发现山奈酚-3-芸香苷、山奈酚-3-葡萄糖苷和飞燕草素-3-羧基修饰芸香苷在3种花色中含量(36%~50%、21%~35%和27%~65%)最多。研究推测:芦丁、山奈酚-3-芸香苷-5-鼠李糖苷和山奈酚-3-p-香豆酰葡萄糖苷为影响蒙农红豆草花色变化的主要成分。     

Contrasting breeding systems in six species of Tillandsia L. (Bromeliaceae) from woody areas of Santa Fe Province: Argentina

The reproductive biology of six native Tillandsia species that co-occurred in woody areas of Santa Fe Province (Argentina) was studied for floral biology, breeding systems and reproductive success. Flower longevity, floral phases, hand self- and cross-pollinations or natural pollinations and fluorescence microscopy observations of post-pollination events were analysed. Also pollen/ovule (P/O) ratio and pre-emergent reproductive success (PERS) were compared between species. In T. aëranthos, T. ixioides and T. meridionalis, self-pollinated flowers mostly failed to form fruits, and fluorescence microscopy studies showed that in selfed pistils pollen tube growth was arrested in the style. It is likely that these species have homomorphic, gametophytic self-incompatibility. In contrast, T. capillaris, T. tricholepis and T. recurvata regularly formed fruits following autonomous self-pollination. Floral traits, the P/O ratios and PERS indices correlate with the breeding systems found in these two groups of species: the three selfing species have inconspicuous closed flowers, and they have low P/O ratios and high PERS values. In contrast, the three self-incompatible (SI) species have conspicuous flowers with relatively high P/O and low PERS values. We described here three new cases of SI in Tillandsia species subgenera Anoplophytum and confirm the autogamous and cleistogamous status in three species of Tillandsia subgenera Diaphoranthema.     

Extreme divergence in floral scent among woodland star species (Lithophragma spp.) pollinated by floral parasites

Backgrounds and Aims

A current challenge in coevolutionary biology is to understand how suites of traits vary as coevolving lineages diverge. Floral scent is often a complex, variable trait that attracts a suite of generalized pollinators, but may be highly specific in plants specialized on attracting coevolved pollinating floral parasites. In this study, floral scent variation was investigated in four species of woodland stars (Lithophragma spp.) that share the same major pollinator (the moth Greya politella, a floral parasite). Three specific hypotheses were tested: (1) sharing the same specific major pollinator favours conservation of floral scent among close relatives; (2) selection favours ‘private channels’ of rare compounds particularly aimed at the specialist pollinator; or (3) selection from rare, less-specialized co-pollinators mitigates the conservation of floral scent and occurrence of private channels.

Methods

Dynamic headspace sampling and solid-phase microextraction were applied to greenhouse-grown plants from a common garden as well as to field samples from natural populations in a series of experiments aiming to disentangle the genetic and environmental basis of floral scent variation.

Key Results

Striking floral scent divergence was discovered among species. Only one of 69 compounds was shared among all four species. Scent variation was largely genetically based, because it was consistent across field and greenhouse treatments, and was not affected by visits from the pollinating floral parasite.

Conclusions

The strong divergence in floral scents among Lithophragma species contrasts with the pattern of conserved floral scent composition found in other plant genera involved in mutualisms with pollinating floral parasites. Unlike some of these other obligate pollination mutualisms, Lithophragma plants in some populations are occasionally visited by generalist pollinators from other insect taxa. This additional complexity may contribute to the diversification in floral scent found among the Lithophragma species pollinated by Greya moths.     

Ultraviolet reflectance mediates pollinator visitation in Mimulus guttatus

Floral colors are widely believed to be an adaptation to attract pollinators. Recently, our understanding of floral reflectance has broadened to include colors that are beyond the spectrum that human eyes can perceive (such as ultraviolet (UV) reflectance), yet we still know relatively little about which plant species reflect UV light or its effectiveness in attracting pollinators. We investigated the effect of UV reflectance in Mimulus guttatus in a number of different populations in British Columbia, Canada. We found that M. guttatus had distinct regions of the corolla where UV light was reflected and absorbed. When we manipulated the degree of contrast between the reflection and absorption area, we found that pollinator visitation was severely disrupted, in terms of frequency and foraging patterns observed. Despite the bright yellow (bee‐green) coloration and visible nectar guides in M. guttatus, we conclude that UV reflectance is critical in pollinator attraction.     

Floral evolution in Lithospermum (Boraginaceae): independent origins of similar flower types

In Lithospermum (Boraginaceae), floral diversity is quite large, with variation in individual quantitative and qualitative traits as well as suites of floral characteristics. The present study utilizes phylogenetic, morphometric and developmental methodologies to investigate patterns of floral evolution, of individual and suites of traits, in the genus and among related genera. The evolutionary patterns of eight quantitative and five qualitative traits were reconstructed, and morphometrics and the evolution of floral morphospace were examined in the genus. Floral developmental patterns were established with light and scanning electron microscopy. Phylogenetic analyses provided evidence that derived flower types have each evolved multiple times, with differences in the manner in which these flower types arose. Floral morphospace has increased throughout the evolution of Lithospermum. Floral developmental patterns and cell lengths of floral organs at anthesis provided evidence that, in Lithospermum, an increase in the length of the sexual organs of flowers involves both longer cells and a greater number of mitotic divisions, but an increase in the length of the corolla is primarily a result of a larger number of cell divisions. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 213–228.     

Can pollination syndromes indicate ecological restoration success in tropical forests?

We evaluated the pollination syndromes of plant species occurring in revegetated patches of riparian Atlantic Forest in order to evaluate the success of restoration process. Between March 2013 and January 2014, the floral traits of all of the flowering plants found in, among four restoration sites of different ages and one reference site, were recorded and used to characterize pollination syndromes. Richness, abundance, and composition of pollination syndromes were related to season, age and width of the forest fragment, species richness and abundance of sampled plants, and also to the quality of the surrounding matrix. There were differences in the composition of syndromes among sampling units and among seasons. Richness and abundance of pollination syndromes varied among climatic periods, the highest values occurred at the end of the dry season and the start of the rainy season. Older, wider, and areas with more plants had higher values of richness and abundance of syndromes. The quality of the surrounding matrix influences only the richness of syndromes. It was concluded that floral traits are good indicators of ecological restoration of riparian forests and that the surrounding matrix contributes to the greater richness of syndromes. However, when planning for active restoration, attention should be given to the proper choice of plant species on the basis of pollination syndromes that should attract pollinators.     

Possible adaptive and non-adaptive radiation in three plant genera in the Japanese archipelago

The adaptive radiation of flowering plants as manifested by the floral diversity has long been considered associated with the diversity of plant–pollinator interactions, because changes in plant–pollinator interactions are hypothesized as one of the major mechanisms driving plant ecological speciation. To understand the relative contributions of various mechanisms for plant radiation, including pollinator changes, it is useful to study a plant group for which comparative study of the species life history across the whole lineage is feasible. To this end, we will focus on the plant lineages that have presumably radiated in the Japanese archipelago, namely, the genera Asimitellaria, Asarum, and Arisaema. By comparing these three genera, we will comment on the possible modes of adaptive radiation and diversification among the endemic flora of Japan.