Search Results
MicroRNAs (miRNAs) related to phytohormone signal transduction and self-incompatibility may play an important role in the xenia effect. However, associated research in this area is still lacking in rabbiteye blueberry (Vaccinium ashei). In this study, we identified miRNAs, predicted their target genes, performed functional enrichment analysis of the target genes, and screened for miRNAs related to phytohormone signaling and self-incompatibility. A total of 491 miRNAs were identified, of which 27 and 67 known miRNAs as well as 274 and 416 new miRNAs were found in the rabbiteye blueberry cultivars Brightwell and Premier, respectively. Compared with ‘Premier’, 31 miRNAs were upregulated and 62 miRNAs were downregulated in ‘Brightwell’. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis indicated that the 4985 target genes predicted were involved in biosynthesis of amino acids, plant–pathogen interaction, and spliceosome pathways. A total of 10, one, one, five, two, five, and two candidate miRNAs related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling, respectively, in rabbiteye blueberry pollen were identified. Further analysis indicated that novel_miR_49 was a candidate miRNA related to self-incompatibility, and their target gene was maker-VaccDscaff21-snap-gene-21.37. In addition, the KEGG enrichment analysis of the target genes of novel_miR_49 showed that they were involved in the ribosome, aminoacyl-tRNA biosynthesis, and glycosylphosphatidylinositol-anchor biosynthesis pathways. The results revealed that the microRNAs of rabbiteye blueberry pollen regulated to phytohormone signal transduction and self-incompatibility signal transduction based on related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling. Results suggest that more research of the effects of miRNAs on regulation of hormone signal transduction and self-incompatibility is necessary for elucidating the molecular mechanism of the xenia effect.
After nearly a decade of development, the scale of blueberry (Vaccinium sp.) cultivation has increased, particularly in south China; however, this region is becoming increasingly challenged by temperature changes during the flowering phenophase. Understanding the effects of temperature on pollen germination and pollen tube growth in blueberry is thus important. Using the rabbiteye blueberry (V. ashei) ‘Brightwell’, different temperature treatments were carried out during open pollination and cross-pollination with the pollen from rabbiteye blueberry ‘Gardenblue’ in field, greenhouse, and controlled temperature experiments over two consecutive years. The differences in pollen germination, pollen tube dynamics, and ovule viability following different treatments were analyzed, and the critical temperatures were calculated using quadratic and modified bilinear equations to quantify the developmental responses to temperature. The results showed that the fruit set of the artificially pollinated plants inside the greenhouse was significantly higher than that outside the greenhouse. Furthermore, pollen germination and pollen tube growth gradually accelerated under the appropriate high-temperature range, resulting in reduced pollen tube travel time to the ovule. However, the percentage of the style traversed by the pollen tube did not increase at temperatures greater than 30 °C, and a high-temperature range could accelerate ovule degeneration. Therefore, impairment of pollen tube growth in the upper half of the style following pollen germination and ovule degeneration constituted important factors leading to reduced fruit setting under short periods of high temperature during the flowering phenophase in rabbiteye blueberry. This work advances our understanding of the effect of temperature on pollen germination, pollen tube growth, ovule longevity, and fruit setting in rabbiteye blueberry, and provides a foundation for continued cultivation and breeding enhancement. The findings propose that the tolerance of rabbiteye blueberry to a certain high-temperature range in the flowering phenophase should inform breeding strategies for temperature resistance and that temperature range is also an important indicator of suitable environments for cultivation to mitigate potential temperature stress.
The xenia effect refers to the phenomenon whereby the pollen genotype directly affects seed and fruit development during the period from fertilization to seed germination, which leads to different characteristics in phenotypic traits. The xenia effect can create differences in the endosperm and embryo formed after double fertilization and can also alter various fruit parameters, such as the fruit-ripening period; the fruit shape, size, and color; the flavor quality, such as sugars and acids; as well as the nutrient quality, such as anthocyanins. The xenia effect manifests in various ways, playing an important role in increasing the yield of fruit trees, improving fruit appearance and internal quality, as well as in directional breeding. Compared with other pomology research areas, our understanding of the xenia effect is still in its infancy. Currently, xenia is classified into two types: xenia and metaxenia. In the former, the direct effects of the pollen genotype are exhibited in the syngamous parts of the ovules; that is, the embryo and endosperm only. In the latter, the effects of the pollen genotype are demonstrated in structures other than the embryo and endosperm; that is, in tissues derived wholly from the mother plant material, in seed parts such as the nucellus and testa, as well as in the carpels and accessory tissues. However, the current classification has various shortcomings. In the present study, we propose a novel classification based on whether the appearance of xenia results from the tissue formed by double fertilization. Three xenia types are proposed: double-fertilization xenia, non–double-fertilization xenia, and combined xenia. The new classification has great theoretical and practical significance for future studies on the xenia effect and its mechanisms and also provides a more effective, broader application of xenia in improving the yield and quality of fruit trees.
Berry fruits produced by Vaccinium (Ericaceae) plants are small but have a signature flavor and have become increasingly popular in the 21st century. However, self-incompatibility (SI) results in a relatively low fruit-set ratio and reduced fruit quality in Vaccinium. In this study, using Vaccinium ashei (V. ashei) styles after cross-pollination (CP) and self-pollination (SP) as material, transcriptomics and gene expression analyses were performed using high-throughput RNA sequencing and quantitative real-time polymerase chain reaction (qRT-PCR). Subsequently, evolutionary analysis and conserved sequences analysis of candidate genes were conducted. Among the 135,324 unigenes, 30,863 were shown to be differentially expressed, and eight randomly selected differentially expressed genes were expressed in the styles at 96 hours after SP and CP. The transcriptomics and qRT-PCR results were significantly correlated, which confirmed the reliability of the differentially expressed genes obtained in our study. Compared with SP96, six differentially expressed ribonuclease T2 family genes were obtained in CP96, which were considered candidates for S-RNase. Additionally, the spatiotemporal and organizational expression trends of six candidates for S-RNase were confirmed by qRT-PCR, and the evolutionary and conservative sequence analysis indicated six candidate S-RNases with the typical S-RNase structure. The spatiotemporal and organizational expression results and evolutionary and conservative sequence analyses of the six candidate S-RNases suggest that SI in V. ashei is likely an S-RNase-mediated gametophytic one. This finding suggests the involvement of novel, previously undiscovered components involved in the V. ashei SI system. These findings help elucidate the molecular mechanisms of SI in rabbiteye blueberry and may also benefit breeding, production, and genomics research in V. ashei and other Vaccinium species.
Salt-affected soils may retard plant growth and cause metabolic alterations. The objective of this study was to investigate the effect of salinity in deep soil on root growth and metabolic changes of tall fescue (Festuca arundinacea). Tall fescue seeds (cv. Houndog V) were planted in polyvinylchloride (PVC) tubes (9 cm diameter × 45 cm long) for 2 months with three treatments of growth substances: (1) control, filled with peat-sand mixtures for full tubes (40 cm height, sand:organic fertilizers = 7:3, w/w); (2) T20, 20 cm saline soil covered with 20 cm organic fertilizers and sand; (3) T30, 30 cm saline soil covered with 10 cm organic fertilizers and sand. Turf quality and vertical shoot growth rate (VSGR) significantly decreased in T30, but not for T20, when compared with the control. Salinity in deep soil obviously inhibited the root growth as indicated by the lower root length, root projected area, root diameter, root fresh, and dry weight, but increased the level of amino acids (Asp, Glu, Ser, Gly, etc.) and soluble sugars (glucose, fructose, sucrose). Root activity in top layer (0–10 cm) of saline soil increased while decreased in deeper layer (20–40 cm) when compared with the control. The increase of root activity and free amino acids in roots from upper layer and the accumulation of soluble sugars in roots from deeper soil layer under salinity conditions were the adaptive responses and regulative mechanisms that for supporting the above-ground plant growth in tall fescue when exposed to deep soil salinity conditions. These results also suggested that a 20 cm of improved mixture of organic fertilizers with sand on the top of saline soil could be sufficient to supply basic space for the normal growth of turfgrass with regular spray irrigation.