Pollen Ultra-Morphology and Pollen Viability Test of Lilium Oriental Hybrids

Ultra-morphology and pollen viability assessment are essential to understand evolutionary ecology and sterility problem, and to design hybridization program in cross-breeding. The pollen ultra-morphology of two Lilium Oriental hybrid cultivars, „Sorbonne‟ and „Siberia‟ were observed using scanning electron microscope. And the pollen germination condition in vitro and four dye tests methods for pollen viability were determined. The results showed that pollens of two Lilium Oriental hybrid cultivars were much alike in ultra-morphology with ellipsoidal shape, reticulate surface decoration and single germination ditch, indicating a close genetic relationship between two cultivars. The suitable medium for pollen germination of two cultivars composed of 10% sucrose, 0.1% boric acid and 0.5% agar. The pollen germination percent reached the highest at 25oC. Although I2-KI stain, TTC stain and peroxidase precipitation methods were not suitable for lily pollen viability test, the pollen viability tested by acetocarmine method were close to that by in vitro pollen germination at suitable condition, which suggested acetocarmine stain can be as a quick test method for pollen viability of Lilium Oriental hybrids. © 2018 Friends Science Publishers

No evidence for transient transformation via pollen magnetofection in several monocot species

ABSTRACTThe development of rapid and efficient transformation methods for many plant species remains an obstacle in both the basic and applied plant sciences. A novel method described by Zhao et al. (2017) used magnetic nanoparticles to deliver DNA into pollen grains of several dicot species, and one monocot (lily), to achieve transformation (“pollen magnetofection”). Using the published protocol, extensive trials by two independent research groups showed no indication of transient transformation success with pollen from two monocots, maize and sorghum. To further address the feasibility of magnetofection, lily pollen was used for side-by-side trials of magnetofection with a proven methodology for transient transformation, biolistics. Using a Green Fluorescent Protein reporter plasmid, transformation efficiency with the biolistic approach averaged 0.7% over three trials. However, the same plasmid produced no recognizable transformants via magnetofection, despite screening >3500 individual pollen grains. We conclude that pollen magnetofection is not effective for transient transformation of pollen for at least three species of monocots, and suggest that efforts to replicate the magnetofection protocol in dicot species would be useful to fully assess its potential.ARISING FROM Zhao et al. Nature Plantshttps://doi.org/10.1038/s41477-017-0063-z (2017)

Analysis of Pollen Allergens in Lily by Transcriptome and Proteome Data

The lily (Lilium spp.) anther contains a lot of pollen. It is not known if lily pollen contains allergens, and therefore screening pollen allergy-related proteins and genes is necessary. The pollen development period of lily ‘Siberia’ was determined by microscope observation. Early mononuclear microspores and mature pollens were used as sequencing materials. The analysis of the pollen transcriptome identified differentially expressed genes (DEGs), e.g., Profilin, Phl p 7 (Polcalcin), Ole e 1, and Phl p 11, which are associated with pollen allergens. The proteome analysis positively verified a significant increase in pollen allergenic protein content. The expression levels of LoProfiilin and LoPolcalcin, annotated as allergen proteins, gradually increased in mature pollen. LoProfiilin and LoPolcalcin were cloned and their open reading frame lengths were 396 bp and 246 bp, which encoded 131 and 81 amino acids, respectively. Amino acid sequence and structure alignment indicated that the protein sequences of LoProfilin and LoPolcalcin were highly conserved. Subcellular localization analysis showed that LoProfilin protein was localized in the cell cytoplasm and nucleus. LoProfilin and LoPolcalcin were highly expressed in mature pollen at the transcriptional and protein levels. A tertiary structure prediction analysis identified LoProfilin and LoPolcalcin as potential allergens in lily pollen.

Perturbation Analysis of Calcium, Alkalinity and Secretion during Growth of Lily Pollen Tubes

Pollen tubes grow by spatially and temporally regulated expansion of new material secreted into the cell wall at the tip of the tube. A complex web of interactions among cellular components, ions and small molecule provides dynamic control of localized expansion and secretion. Cross-correlation studies on oscillating lily (Lilium formosanum Wallace) pollen tubes showed that an increase in intracellular calcium follows an increase in growth, whereas the increase in the alkaline band and in secretion both anticipate the increase in growth rate. Calcium, as a follower, is unlikely to be a stimulator of growth, whereas the alkaline band, as a leader, may be an activator. To gain further insight herein we reversibly inhibited growth with potassium cyanide (KCN), and followed the re-establishment of calcium, pH and secretion patterns as growth resumed. While KCN markedly slows growth and causes the associated gradients of calcium and pH to sharply decline, its removal allows growth and vital processes to fully recover. The calcium gradient reappears before growth restarts, however it is preceded by both the alkaline band and secretion, in which the alkaline band is slightly advanced over secretion. Thus the pH gradient, rather than the tip-focused calcium gradient, may regulate pollen tube growth.