Key message Gymnosperm pollen grains release ATP to the extracellular matrix which is essential for the initiation of pollen germination and tube growth. Abstract Extracellular ATP (eATP) is an important signaling compound involved in various processes of animal and angiosperm cells. However, the role played by eATP in gymnosperm cells remains unclear. Using a bioluminescence assay, we found that pollen grains of Picea meyeri released ATP to the extracellular matrix before germination and during tube elongation. The addition of further exogenous ATP or an apyrase inhibitor to pollen suspensions inhibited germination and pollen tube elongation. Exogenous apyrase (which hydrolyzes eATP released from pollen per se) exerted a similar inhibitory effect. Moreover, incubation of pollen suspensions with purinoceptor inhibitors prevented germination. ATP intensified the influx of Ca 2? after germination, which was abrogated by purinoceptor inhibitors. Confocal microscopy revealed that the microfilament pattern became disorganized in pollen tubes when exposed to ATP. Together, our findings suggest that optimum concentration of eATP is essential for initiation of pollen germination, and eATP signaling regulates pollen tube growth by activating purinoceptors to increase Ca 2? influx, thus modulating microfilament organization, which, in turn, is essential for pollen germination and tube growth. Hence, we provide a mechanistic framework for the role played by eATP in pollen germination and tube growth.
Histone deacetylase (HDAC) is a crucial component in the regulation of gene expression in various cellular processes in animal and plant cells. HDAC has been reported to play a role in embryogenesis. However, the effect of HDAC on androgamete development remains unclear, especially in gymnosperms. In this study, we used the HDAC inhibitors trichostatin A (TSA) and sodium butyrate (NaB) to examine the role of HDAC in Picea wilsonii pollen germination and pollen tube elongation. Measurements of the tip-focused Ca2+ gradient revealed that TSA and NaB influenced this gradient. Immunofluorescence showed that actin filaments were disrupted into disorganized fragments. As a result, the vesicle trafficking was disturbed, as determined by FM4-64 labeling. Moreover, the distribution of pectins and callose in cell walls was significantly altered in response to TSA and NaB. Our results suggest that HDAC affects pollen germination and polarized pollen tube growth in Picea wilsonii by affecting the intracellular Ca2+ concentration gradient, actin organization patterns, vesicle trafficking, as well as the deposition and configuration of cell wall components.
Tiegun yam is a typical food and medicine agricultural product, which has the effects of nourishing the kidney and benefitting the lungs. The quality and price of Tiegun yam are affected by its origin, and counterfeiting and adulteration are common. Therefore, it is necessary to establish a method to identify the origin and index component contents of Tiegun yam. Hyperspectral imaging combined with chemometrics was used, for the first time, to explore and implement the identification of origin and index component contents of Tiegun yam. The origin identification models were established by partial least squares-discriminant analysis (PLS-DA), support vector machine (SVM), and random forest (RF) using full wavelength and feature wavelength. Compared with other models, MSC-PLS-DA is the best model, and the accuracy of the training set and prediction set is 100% and 98.40%. Partial least squares regression (PLSR), random forest (RF), and support vector regression (SVR) models were used to predict the contents of starch, polysaccharide, and protein in Tiegun yam powder. The optimal residual predictive deviation (RPD) values of starch, polysaccharide, and protein prediction models selected in this study were 5.21, 3.21, and 2.94, respectively. The characteristic wavelength extracted by the successive projections algorithm (SPA) method can achieve similar results as the full-wavelength model. These results confirmed the application of hyperspectral imaging (HSI) in the identification of the origin and the rapid nondestructive prediction of starch, polysaccharide, and protein contents of Tiegun yam powder. Therefore, the HSI combined with the chemometric method was available for conveniently and accurately determining the origin and index component contents of Tiegun yam, which can expect to be an attractive alternative method for identifying the origin of other food.
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