The PIF1-miR408-PLANTACYANIN Repression Cascade Regulates Light-Dependent Seed Germination

Abstract Light-dependent seed germination is a vital process for many seed plants. A decisive event in light-induced germination is degradation of the central repressor PHYTOCHROME INTERACTING FACTOR 1 (PIF1). The balance between gibberellic acid (GA) and abscisic acid (ABA) helps to control germination. However, the cellular mechanisms linking PIF1 turnover to hormonal balancing remain elusive. Here, employing far-red light-induced Arabidopsis thaliana seed germination as the experimental system, we identified PLANTACYANIN (PCY) as an inhibitor of germination. It is a blue copper protein associated with the vacuole that is both highly expressed in mature seeds and rapidly silenced during germination. Molecular analyses showed that PIF1 binds to the miR408 promoter and represses miR408 accumulation. This in turn posttranscriptionally modulates PCY abundance, forming the PIF1-miR408-PCY repression cascade for translating PIF1 turnover to PCY turnover during early germination. Genetic analysis, RNA-sequencing, and hormone quantification revealed that PCY is necessary and sufficient to maintain the PIF1-mediated seed transcriptome and the low-GA-high-ABA state. Furthermore, we found that PCY domain organization and regulation by miR408 are conserved features in seed plants. These results revealed a cellular mechanism whereby PIF1-relayed external light signals are converted through PCY turnover to internal hormonal profiles for controlling seed germination.

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The PIF1-MIR408-Plantacyanin Repression Cascade Regulates Light Dependent Seed Germination

10.1101/2020.07.20.212340 ◽

2020 ◽

Author(s):

Anlong Jiang ◽

Zhonglong Guo ◽

Jiawei Pan ◽

Yan Zhuang ◽

Daqing Zuo ◽

...

Keyword(s):

Seed Germination ◽

Red Light ◽

Experimental System ◽

Seed Plants ◽

Cellular Mechanisms ◽

Light Sensing ◽

Early Germination ◽

Light Signals ◽

Necessary And Sufficient ◽

Storage Vacuole

ABSTRACTLight-sensing seed germination is a vital process for the seed plants. A decisive event in light-induced germination is degradation of the central repressor PHYTOCHROME INTERACTING FACTOR1 (PIF1). It is also known that the balance between gibberellic acid (GA) and abscisic acid (ABA) critically controls germination. But the cellular mechanisms linking PIF1 turnover to hormonal rebalancing remain elusive. Here, employing far-red light-induced Arabidopsis seed germination as the experimental system, we identified Plantacyanin (PLC) as an inhibitor of germination, which is a storage vacuole-associated blue copper protein highly expressed in mature seed and rapidly silenced during germination. Molecular analyses showed that PIF1 directly binds to the MIR408 promoter and represses miR408 accumulation, which in turn post-transcriptionally modulates PLC abundance, thus forming the PIF1-MIR408-PLC repression cascade for translating PIF1 turnover to PLC turnover during early germination. Genetic analysis, RNA-sequencing, and hormone quantification revealed that PLC is necessary and sufficient to maintain the PIF1-mediated seed transcriptome and the low-GA-high-ABA state. Furthermore, we found that PLC domain organization and regulation by miR408 are conserved features in seed plants. These results unraveled a cellular mechanism whereby PIF1-relayed external light signals are converted through PLC-based copper mobilization into internal hormonal profiles for controlling seed germination.

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Asymbiotic germination of Vanilla planifolia in relation to the timing of seed collection and seed pretreatments

Botanical Studies ◽

10.1186/s40529-021-00311-y ◽

2021 ◽

Vol 62 (1) ◽

Author(s):

Chih-Hsin Yeh ◽

Kai-Yi Chen ◽

Yung-I. Lee

Keyword(s):

Seed Germination ◽

Seed Development ◽

Seed Coat ◽

Germination Percentage ◽

Vanilla Planifolia ◽

Outermost Layer ◽

Seed Collection ◽

Seed Pretreatment ◽

Immature Seeds ◽

Mature Seeds

Abstract Background Vanilla planifolia is an important tropical orchid for production of natural vanilla flavor. Traditionally, V. planifolia is propagated by stem cuttings, which produces identical genotype that are sensitive to virulent pathogens. However, propagation with seed germination of V. planifolia is intricate and unstable because the seed coat is extremely hard with strong hydrophobic nature. A better understanding of seed development, especially the formation of impermeable seed coat would provide insights into seed propagation and conservation of genetic resources of Vanilla. Results We found that soaking mature seeds in 4% sodium hypochlorite solution from 75 to 90 min significantly increased germination. For the culture of immature seeds, the seed collection at 45 days after pollination (DAP) had the highest germination percentage. We then investigated the anatomical features during seed development that associated with the effect of seed pretreatment on raising seed germination percentage. The 45-DAP immature seeds have developed globular embryos and the thickened non-lignified cell wall at the outermost layer of the outer seed coat. Seeds at 60 DAP and subsequent stages germinated poorly. As the seed approached maturity, the cell wall of the outermost layer of the outer seed coat became lignified and finally compressed into a thick envelope at maturity. On toluidine blue O staining, the wall of outer seed coat stained greenish blue, indicating the presence of phenolic compounds. As well, on Nile red staining, a cuticular substance was detected in the surface wall of the embryo proper and the innermost wall of the inner seed coat. Conclusion We report a reliable protocol for seed pretreatment of mature seeds and for immature seeds culture based on a defined time schedule of V. plantifolia seed development. The window for successful germination of culturing immature seed was short. The quick accumulation of lignin, phenolics and/or phytomelanins in the seed coat may seriously inhibit seed germination after 45 DAP. As seeds matured, the thickened and lignified seed coat formed an impermeable envelope surrounding the embryo, which may play an important role in inducing dormancy. Further studies covering different maturity of green capsules are required to understand the optimal seed maturity and germination of seeds.

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Asymbiotic Germination of Mature Seeds and the Seed Development of Vanilla Planifolia

10.21203/rs.3.rs-138206/v1 ◽

2021 ◽

Author(s):

Chih-Hsin Yeh ◽

Kai-Yi Chen ◽

Yung-I Lee

Keyword(s):

Cell Wall ◽

Seed Germination ◽

Seed Development ◽

Seed Coat ◽

Germination Percentage ◽

Vanilla Planifolia ◽

Outermost Layer ◽

Seed Pretreatment ◽

Immature Seeds ◽

Mature Seeds

Abstract Background: Vanilla planifolia is an important tropical orchid for production of natural vanilla flavor. Traditionally, V. planifolia is propagated by stem cuttings, which produces identical genotype that are sensitive to virulent pathogens. However, sexual propagation with seed germination of V. planifolia is intricate and unstable because of the extremely hard seed coat. A better understanding of seed development, especially the formation of impermeable seed coat would provide insights into seed propagation and conservation of genetic resources of Vanilla.Results: We found that soaking mature seeds in 4 % sodium hypochlorite solution from 75 to 90 min significantly increased germination and that immature seeds collected at 45 days after pollination (DAP) had the highest germination percentage. We then investigated the anatomical features during seed development that associated with the effect of seed pretreatment on raising seed germination percentage. The 45-DAP immature seeds have developed globular embryos and the thickened non-lignified cell wall at the outermost layer of the outer seed coat. After 60 DAP, the cell wall of the outermost layer of the outer seed coat became lignified and finally compressed into a thick envelope. These features matches the significant decreases of immature seed germination percentage after 60 DAP. Conclusion: We report a reliable protocol for seed pretreatment of mature seeds and for immature seeds culture based on a defined time schedule of V. plantifolia seed development. The thickened and lignified seed coat formed an impermeable envelope surrounding the embryo, and might play an important role in seed dormancy of V. plantifolia.

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The counteracting effect of potassium cyanide in sodium azide-inhibited germination of Paulownia tomentosa Steud. seeds

Archives of Biological Sciences ◽

10.2298/abs0501029z ◽

2005 ◽

Vol 57 (1) ◽

pp. 29-34 ◽

Cited By ~ 1

Author(s):

Suzana Zivkovic ◽

Dragoljub Grubisic ◽

Zlatko Giba ◽

Radomir Konjevic

Keyword(s):

Seed Germination ◽

Light Pulse ◽

Sodium Azide ◽

Incubation Medium ◽

Red Light ◽

Potassium Cyanide ◽

Inhibitory Effect ◽

Escape Time ◽

Paulownia Tomentosa ◽

Respiratory Inhibitors

The effect of some respiratory inhibitors on light-induced Paulownia tomentosa Steud. seed germination was studied. Millimolar solution of sodium azide was sufficient to completely prevent germination induced by a 5-min red light pulse. The inhibitory effect of azide was absent if seeds were rinsed before phytochrome activation by light. Sodium azide was effective only if present in the period of Pfr activity. The escape time from azide inhibition compared to the escape from far-red light action, was delayed for about 24 hours. When azide was applied after phytochrome activation, its effect depended on how long it was present in the incubation medium. The removal of azide allowed full restoration of germination by another red light pulse and the far-red escape time did not differ from the escape of untreated, i.e. water-imbibed seeds. Potassium cyanide alone did not produce any effect in light-stimulated germination of these seeds. However, it counteracted the inhibitory effect of azide in light-stimulated germination, if applied simultaneously at a concentration three times higher.

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Arabidopsis chloroplast J protein DJC75/CRRJ mediates nitrate-promoted seed germination in the dark

Annals of Botany ◽

10.1093/aob/mcaa040 ◽

2020 ◽

Vol 125 (7) ◽

pp. 1091-1099

Author(s):

Huai-Syuan Ciou ◽

Yu-Lun Tsai ◽

Chi-Chou Chiu

Keyword(s):

Arabidopsis Thaliana ◽

Seed Germination ◽

Germination Rate ◽

Red Light ◽

Phytochrome B ◽

Biosynthetic Gene ◽

Unknown Mechanism ◽

J Domain ◽

Domain Protein ◽

J Protein

Abstract Background and Aims Nitrate can stimulate seed germination of many plant species in the absence of light; however, the molecular mechanism of nitrate-promoted seed germination in the dark remains largely unclear and no component of this pathway has been identified yet. Here, we show that a plastid J-domain protein, DJC75/CRRJ, in arabidopsis (Arabidopsis thaliana) is important for nitrate-promoted seed germination in the dark. Methods The expression of DJC75 during imbibition in the dark was investigated. The seed germination rate of mutants defective in DJC75 was determined in the presence of nitrate when light cues for seed germination were eliminated by the treatment of imbibed seeds with a pulse of far-red light to inactivate phytochrome B (phyB), or by assaying germination in the dark with seeds harbouring the phyB mutation. The germination rates of mutants defective in CRRL, a J-like protein related to DJC75, and in two chloroplast Hsp70s were also measured in the presence of nitrate in darkness. Key Results DJC75 was expressed during seed imbibition in the absence of light. Mutants defective in DJC75 showed seed germination defects in the presence of nitrate when light cues for seed germination were eliminated. Mutants defective in CRRL and in two chloroplast Hsp70s also exhibited similar seed germination defects. Upregulation of gibberellin biosynthetic gene GA3ox1 expression by nitrate in imbibed phyB mutant seeds was diminished when DJC75 was knocked out. Conclusions Our data suggest that plastid J-domain protein DJC75 regulates nitrate-promoted seed germination in the dark by upregulation of expression of the gibberellin biosynthetic gene GA3ox1 through an unknown mechanism and that DJC75 may work in concert with chloroplast Hsp70s to regulate nitrate-promoted seed germination. DJC75 is the first pathway component identified for nitrate-promoted seed germination in the dark.

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Contrasting seed germination responses to red and far-red light in Leptospermum scoparium and Melicytus ramiflorus

Functional Plant Biology ◽

10.1071/pp00024 ◽

2000 ◽

Vol 27 (11) ◽

pp. 1069

Author(s):

Helen Herron ◽

John Clemens ◽

Dennis H. Greer

Keyword(s):

Seed Germination ◽

Red Light ◽

Green Light ◽

Photon Flux ◽

Short Term ◽

Short Term Exposure ◽

Subsequent Exposure ◽

R:Fr Ratio ◽

Leptospermum Scoparium

Effects of red light (R) and far-red light (FR), and selected photon flux densities (PFD) of photosynthetically active radiation (PAR) on seed germination in the photoblastic, primary colonising species Leptospermum scoparium J. R. et G. Forst. and the late secondary successional Melicytus ramiflorus J. R. et G. Forst. were studied. A continuous R dose response curve forL. scoparium germination was developed, unifying data from experiments using long-term exposure to PAR with those following short-term exposure to R. The threshold R dose needed to effect germination was ~0.1 mmol m –2 , and the response was saturated at 1000 mmol m –2 . Stimulation of germination by R was reversed by a subsequent exposure to FR. These features are consistent with a low-fluence response mediated by phytochrome B. FR reversal of germination was achieved at a dose two orders of magnitude lower than that of R required to induce initial germination. However, when both R and FR were provided simultaneously, the FR dose needed to even partially inhibit germination (34% compared to > 95% in controls) was two orders of magnitude higher than the R dose (R:FR ratio = 0.007). Germination in L. scoparium was also stimulated in up to 12% of seed upon diurnal exposure to FR, or by green light (~2 mol m –2 ), indicating a very-low-fluence response mediated by phytochrome A also operating in this species. In contrast, seed germination in M. ramiflorus was relatively unresponsive to R, and secondary dormancy was induced by high PFD (515 mol m –2 s –1 ).

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LPIAT, a lyso-Phosphatidylinositol Acyltransferase, Modulates Seed Germination in Arabidopsis thaliana through PIP Signalling Pathways and is Involved in Hyperosmotic Response

International Journal of Molecular Sciences ◽

10.3390/ijms21051654 ◽

2020 ◽

Vol 21 (5) ◽

pp. 1654

Author(s):

Denis Coulon ◽

Lionel Faure ◽

Magali Grison ◽

Stéphanie Pascal ◽

Valérie Wattelet-Boyer ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Seed Germination ◽

Lipid Synthesis ◽

Strong Increase ◽

In Planta ◽

Acyltransferase Activity ◽

Chain Acyl ◽

Phosphatidylinositol Phosphates ◽

Mature Seeds

Lyso-lipid acyltransferases are enzymes involved in various processes such as lipid synthesis and remodelling. Here, we characterized the activity of an acyltransferase from Arabidopsis thaliana (LPIAT). In vitro, this protein, expressed in Escherichia coli membrane, displayed a 2-lyso-phosphatidylinositol acyltransferase activity with a specificity towards saturated long chain acyl CoAs (C16:0- and C18:0-CoAs), allowing the remodelling of phosphatidylinositol. In planta, LPIAT gene was expressed in mature seeds and very transiently during seed imbibition, mostly in aleurone-like layer cells. Whereas the disruption of this gene did not alter the lipid composition of seed, its overexpression in leaves promoted a strong increase in the phosphatidylinositol phosphates (PIP) level without affecting the PIP2 content. The spatial and temporal narrow expression of this gene as well as the modification of PIP metabolism led us to investigate its role in the control of seed germination. Seeds from the lpiat mutant germinated faster and were less sensitive to abscisic acid (ABA) than wild-type or overexpressing lines. We also showed that the protective effect of ABA on young seedlings against dryness was reduced for lpiat line. In addition, germination of lpiat mutant seeds was more sensitive to hyperosmotic stress. All these results suggest a link between phosphoinositides and ABA signalling in the control of seed germination

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Quantitative trait loci associated with lettuce seed germination under different temperature and light environments

Genome ◽

10.1139/g08-077 ◽

2008 ◽

Vol 51 (11) ◽

pp. 928-947 ◽

Cited By ~ 27

Author(s):

Eiji Hayashi ◽

Natsuyo Aoyama ◽

David W. Still

Keyword(s):

Quantitative Trait Loci ◽

Seed Germination ◽

Path Analysis ◽

Quantitative Trait ◽

Germination Rate ◽

Red Light ◽

Seed Maturation ◽

Lettuce Seed ◽

Factors Affecting ◽

Trait Loci

Temperature and light are primary environmental cues affecting seed germination. To elucidate the genetic architecture underlying lettuce ( Lactuca sativa L.) seed germination under different environmental conditions, an F8 recombinant inbred line population consisting of 131 families was phenotyped for final germination and germination rate. Seeds were imbibed in water at 20 °C under continuous red light (20-Rc), 20 °C continuous dark (20-Dc), 31.5 °C continuous red light (31.5-Rc), 31.5 °C continuous dark (31.5-Dc), or 20 °C far-red light for 24 h followed by continuous dark (20-FRc-Dc). Thirty-eight quantitative trait loci (QTL) were identified from two seed maturation environments: 10 for final germination and 28 for germination rate. The amount of variation attributed to an individual QTL ranged from 9.3% to 17.2% and from 5.6% to 26.2% for final germination and germination rate, respectively. Path analysis indicated that factors affecting germination under 31.5-Rc or 31.5-Dc are largely the same, and these appear to differ from those employed under 20-FRc-Dc. QTL and path analysis support the notion of common and unique factors for germination under diverse temperature and light regimes. A highly significant effect of the seed maturation environment on subsequent germination capacity under environmental stress was observed.

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