Cytosolic free Ca 21 and actin microfilaments play crucial roles in regulation of pollen germination and tube growth. The focus of this study is to test the hypothesis that Ca 21 channels, as well as channel-mediated Ca 21 influxes across the plasma membrane (PM) of pollen and pollen tubes, are regulated by actin microfilaments and that cytoplasmic Ca 21 in pollen and pollen tubes is consequently regulated. In vitro Arabidopsis (Arabidopsis thaliana) pollen germination and tube growth were significantly inhibited by Ca 21 channel blockers La 31 or Gd 31 and F-actin depolymerization regents. The inhibitory effect of cytochalasin D (CD) or cytochalasin B (CB) on pollen germination and tube growth was enhanced by increasing external Ca 21 . Ca 21 fluorescence imaging showed that addition of actin depolymerization reagents significantly increased cytoplasmic Ca 21 levels in pollen protoplasts and pollen tubes, and that cytoplasmic Ca 21 increase induced by CD or CB was abolished by addition of Ca 21 channel blockers. By using patch-clamp techniques, we identified the hyperpolarization-activated inward Ca 21 currents across the PM of Arabidopsis pollen protoplasts. The activity of Ca 21 -permeable channels was stimulated by CB or CD, but not by phalloidin. However, preincubation of the pollen protoplasts with phalloidin abolished the effects of CD or CB on the channel activity. The presented results demonstrate that the Ca 21 -permeable channels exist in Arabidopsis pollen and pollen tube PMs, and that dynamic actin microfilaments regulate Ca 21 channel activity and may consequently regulate cytoplasmic Ca 21 .The primary function of pollen and pollen tubes is to deliver sperms to egg apparatus for double fertilization that is required for sexual reproduction of flowering plants. Pollen germination and pollen tube growth are a continuous and highly polarized process characteristic of tip growth; thus pollen and pollen tubes provide an ideal model system for the study of cell polarity control and tip growth. It is well known that extracellular Ca 21 is required for pollen germination and tube growth (for review, see Steer and Steer, 1989;Taylor and Hepler, 1997;Malhó , 1998;Franklin-Tong, 1999), which indicates a possible involvement of Ca 21 influx in pollen germination and tube growth. Upon pollen hydration and germination, cytoplasmic Ca 21 concentration ([Ca 21 ] i ) at the germinal aperture where the pollen tube emerges increases to a higher level than other regions, and a tip-focused Ca 21 gradient is then established and sustained while a pollen tube grows forward (Rathore et al., 1991;Pierson et al., 1994;Feijó et al., 1995). Disruption or modification of the Ca 21 gradient inhibits pollen tube growth (Miller et al., 1992) or changes its growth direction (Malhó and Trewavas, 1996). The tip-focused Ca 21 gradient oscillates in the pollen tubes of lily (Lilium longiflorum) and other species (Holdaway-Clarke et al., 1997;Messerli and Robinson, 1997;Messerli et al., 2000). Ca 21 mobilization from intracellular Ca...

Botryosphaeriaceae are an important fungal family that cause woody plant diseases worldwide. Recent studies have established a correlation between environmental factors and disease expression; however, less is known about factors that trigger these diseases. The current study reports on the 43.3 Mb de novo genome of Lasiodiplodia theobromae and five other genomes of Botryosphaeriaceae pathogens. Botryosphaeriaceous genomes showed an expansion of gene families associated with cell wall degradation, nutrient uptake, secondary metabolism and membrane transport, which contribute to adaptations for wood degradation. Transcriptome analysis revealed that genes involved in carbohydrate catabolism, pectin, starch and sucrose metabolism, and pentose and glucuronate interconversion pathways were induced during infection. Furthermore, genes in carbohydrate-binding modules, lysine motif domain and the glycosyl hydrolase gene families were induced by high temperature. Among these genes, overexpression of two selected putative lignocellulase genes led to increased virulence in the transformants. These results demonstrate the importance of high temperatures in opportunistic infections. This study also presents a set of Botryosphaeriaceae-specific effectors responsible for the identification of virulence-related pathogen-associated molecular patterns and demonstrates their active participation in suppressing hypersensitive responses. Together, these findings significantly expand our understanding of the determinants of pathogenicity or virulence in Botryosphaeriaceae and provide new insights for developing management strategies against them.

Whether the effect of migration-selection-drift equilibrium on population structure is governed by spatial or environmental differences is usually elucidated by isolation-by-distance (IBD), isolation-by-environment (IBE), and isolation-by-resistance (IBR) tests. The population structure of Ammopiptanthus mongolicus , a broad-leaved evergreen psammophyte in eastern Central Asia, was previously thought to follow an isolation by distance pattern. However, recent studies have emphasized the effects of environmental factors on its growth and distribution, suggesting an important influence of local adaptation on the genetic structure of the species. Using inter-simple sequence repeat (ISSR) markers, we verified the previously inferred low intra-population variation and high inter-population differentiation. However, in contrast to previous studies, the results of partial Mantel tests and a maximum likelihood population effects mixed model (MLPE) suggested that local climate differences, rather than geographic distances or resistance distances, are the main factor affecting population differentiation. Further analysis with removal of multicollinear climatic variables and univariate MLPE found that summer and winter precipitation were crucial for shaping the current population genetic structure. Since local precipitation is related to the regeneration, colonization, and overwintering survival of A. mongolicus , its influence on demographic change may explain its effect on the population genetic structure. In addition, precipitation is related to terrain despite westward decreases, which explains the independence of genetic difference and geographic distance. The identified role of IBE suggests that collecting germplasm resources from genetically differentiated populations could be a more effective strategy to preserve the overall genetic diversity of the species than the establishment of corridors to enhance gene flow among populations.

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BackgroundAtKinesin-13A is an internal-motor kinesin from Arabidopsis (Arabidopsis thaliana). Previous immunofluorescent results showed that AtKinesin-13A localized to Golgi stacks in plant cells. However, its precise localization and biological function in Golgi apparatus is unclear.ResultsIn this paper, immunofluorescent labeling and confocal microscopic observation revealed that AtKinesin-13A was co-localized with Golgi stacks in Arabidopsis root tip cells. Immuno-electron microscopic observations indicated that AtKinesin-13A is primarily localized on Golgi-associated vesicles in Arabidopsis root-cap cells. By T-DNA insertion, the inactivation of the AtKinesin-13A gene (NM-112536) resulted in a sharp decrease of size and number of Golgi vesicles in root-cap peripheral cells. At the same time, these cells were vacuolated in comparison to the corresponding cells of the wild type.ConclusionThese results suggest that AtKinesin-13A decorates Golgi-associated vesicles and may be involved in regulating the formation of Golgi vesicles in the root-cap peripheral cells in Arabidopsis.