Potassium-Dependent Increase in RNA and Protein Synthesis in the Early Phase of Incubation of the Thermodormant Phacelia tanacetifolia Seeds

Characterization of physiological and molecular processes associated with potato response to Zebra chip disease

Transcriptional analyses identified molecular mechanisms associated with the response of leaf and root potato tissues to 'Candidatus. Liberibacter solanacearum' (Lso) infection, presumptive causal agent of zebra chip disease (ZC). Putative Lso infection affected several host processes including defense response-, regulation-, starch metabolism- and energy production-related processes. Interestingly, while proteinase inhibitors were strongly upregulated in leaf tissues, a concomitant downregulation was observed in root tissues. Quantitative polymerase chain reaction (qPCR) analysis suggests that alternative splicing might play a role. Furthermore, the transcriptional expression of redox homeostasis-related genes, including superoxide dismutase, showed the most inconsistent response to Lso in leaf and root tissues, highlighting potential targets of Lso susceptibility. Additionally, a net increase in gene expression in ZC-affected tissues despite the concomitant downregulation of photosynthesis-related processes, suggests a putative Lso-mediated low resource-use-efficiency. Subsequent nutritional analyses revealed a hypothesized Lso-mediated increase in nutrient accumulation, particularly a 210 and 108% increases in the potassium concentration of ZC-affected leaf and root tissues, respectively, suggesting an important role for potassium in ZC pathophysiology. This study highlights insights of above and below ground tissues in molecular and physiological aspects associated with potato response to ZC.

Reversal of the inhibitory effect of light and high temperature on germination of Phacelia tanacetifolia seeds by melatonin

Possible role of melatonin in the germination of negatively photoblastic and thermosensitive seeds of Phacelia tanacetifolia Benth was studied. Final germination percentage (FGP) was determined in the presence or absence of light at various temperatures, ranging from 0 to 40°C. The highest FGP was determined as 48.7% and 92% at temperature of 15°C in the presence and absence of light, respectively. Seeds were primed with 1% KNO(3) containing various concentrations (0.3, 1, 6, 12, 30, 60, or 90 μM) of melatonin for 2 days at 15°C in darkness. Primed seeds were germinated at an inhibitory temperature of 30°C, and results were compared to those occurring at the optimum temperature of 15°C under both light and no light conditions. Melatonin incorporated into priming medium significantly reversed the inhibitory effects of light and high temperature. Germination was elevated from 2.5% to 52% of FGP for seeds primed in the presence of 6 μM melatonin in darkness at 30°C, while 1 μM melatonin had the highest FGP (21.0%) in the presence of light at 30°C. The highest FGP (47.5%) was obtained from seeds primed in the presence of 0.3 μM melatonin under the light condition at 15°C, while untreated seeds had 1.5% of FGP. The fastest seed germination was determined from seeds primed in the presence of 0.3 μM melatonin (G(50) = 0.56 days) at 15°C in darkness. The possible roles of melatonin in promoting germination parameters of photo- and thermosensitive seed germination are discussed.