Hydro-Electro Hybrid Priming Promotes Carrot (Daucus carota L.) Seed Germination by Activating Lipid Utilization and Respiratory Metabolism

Synergistic effects of gamma-aminobutyric acid and melatonin on seed germination and cadmium tolerance in tomato

The effects of exogenous γ-aminobutyric acid (GABA) and melatonin (MT) on tomato seed germination and shoot growth exposed to cadmium stress were investigated. On the one hand, treatment with MT (10-200 μM) or GABA (10-200 μM) alone could significantly relieve cadmium stress in tomato seedlings, which is reflected in increasing the germination rate, vigor index, fresh weight, dry weight and radicle lengths of tomato seeds, as well as the soluble content compared to the absence of exogenous treatment, and the alleviating effect reached the peak in the 200 µM GABA or 150 µM MT alone. On the other hand, exogenous MT and GABA showed synergistic effects on the germination of tomato seed under cadmium stress. Moreover, the application of 100 µM GABA combined with 100 µM MT markedly decreased the contents of Cd and MDA by upregulating the activities of antioxidant enzymes, thereby alleviating the toxic effect of cadmium stress on tomato seeds. Collectively, the combinational strategy showed significant positive effects on seed germination and cadmium stress resistance in tomato.

Transcriptome and proteome analyses reveal the potential mechanism of seed dormancy release in Amomum tsaoko during warm stratification

BACKGROUND

In Amomum tsaoko breeding, the low germination rate is the major limitation for their large-scale reproduction. We found that warm stratification was an effective treatment to break the seed dormancy of A. tsaoko prior to sowing and could be an important component of improving breeding programs. The mechanism of seed dormancy release during warm stratification remains unclear. Therefore, we studied the differences between transcripts and proteomes at 0, 30, 60, and 90 days of warm stratification, to identify some regulatory genes and functional proteins that may cause seed dormancy release in A. tsaoko and reveal their regulatory mechanism.

RESULTS

RNA-seq was performed for the seed dormancy release process, and the number of differentially expressed genes (DEGs) was 3196 in three dormancy release periods. Using TMT-labelling quantitative proteome analysis, a total of 1414 proteins were defined as differentially expressed proteins (DEPs). Functional enrichment analyses revealed that the DEGs and DEPs were mainly involved in signal transduction pathways (MAPK signaling, hormone) and metabolism processes (cell wall, storage and energy reserves), suggesting that these differentially expressed genes and proteins are somehow involved in response to seed dormancy release process, including MAPK, PYR/PYL, PP2C, GID1, GH3, ARF, AUX/IAA, TPS, SPS, and SS. In addition, transcription factors ARF, bHLH, bZIP, MYB, SBP, and WRKY showed differential expression during the warm stratification stage, which may relate to dormancy release. Noteworthy, XTH, EXP, HSP and ASPG proteins may be involved in a complex network to regulate cell division and differentiation, chilling response and the seed germination status in A. tsaoko seed during warm stratification.

CONCLUSION

Our transcriptomic and proteomic analysis highlighted specific genes and proteins that warrant further study in fully grasping the precise molecular mechanisms that control the seed dormancy and germination of A. tsaoko. A hypothetical model of the genetic regulatory network provides a theoretical basis for overcoming the physiological dormancy in A. tsaoko in the future.

Biopriming of seed with plant growth-promoting bacteria for improved germination and seedling growth

Several seed priming methods can be used to improve seed germination, seedling vigor, and to overcome abiotic stress. In addition to these benefits, only the biopriming method provides the additional benefit of biotic stress management, earning it special attention. Seed biopriming is useful in almost all crops around the world and is an environmentally friendly alternative to chemical fungicides. Biopriming usually refers to use of beneficial microorganisms, in particular plant growth-promoting bacteria (PGPB) able to survive under various harsh environmental conditions. In this study, various bacterial strains were isolated from samples of different origins, i.e., rhizospheric soil, desert sand, and sea mud. Preliminary screening of 156 bacterial isolates was conducted on the basis of their potassium (K), phosphorus (P) solubilization ability, and production of plant growth hormone, i.e., indole acetic acid (IAA). The most efficient bacteria were identified by 16S rRNA gene nucleotide sequences and further examined for their ACC deaminase activity, ammonia production, and biocontrol activity (defined via chitinolytic activity, HCN, and siderophores production). Finally, carrot seed germination assay was conducted with 10 shortlisted most potent isolates. 68.6, 58.3, and 66.7% of tested bacterial isolates were capable of P, K, and Zn solubilization, respectively. Klebsiella aerogenes AF3II1 showed the highest P and K solubilization, while isolate AF4II5, AF7II3, and PC3 showed the highest IAA synthesis ability. Serratia plymuthica EDC15 and Pseudomonas putida AF1I1 showed the strongest chitinolytic and siderophore production activity, respectively. Seven isolates demonstrated strong HCN production ability. Five isolates improved carrot seed germination. Only selected isolates with plant growth-promoting properties can improve carrot germination. The results of this study demonstrate that mainly auxins are involved in seed germination. Furthermore, the data suggest that phosphate solubilization ability may play an additional role in seed germination.

Non-chlorophyllous and crypto-chlorophyllous fern spores differ in their mobilisation of fatty acids during priming

During fern spore germination, lipid hydrolysis primarily provides the energy to activate their metabolism. In this research, fatty acids (linoleic, oleic, palmitic and stearic) were quantified in the spores exposed or not to priming (hydration-dehydration treatments). Five fern species were investigated, two from xerophilous shrubland and three from a cloud forest. We hypothesised that during the priming hydration phase, the fatty acids profile would change in concentration, depending on the spore type (non-chlorophyllous and crypto-chlorophyllous). The fatty acid concentration was determined by gas chromatograph-mass spectrometer. Chlorophyll in spores was vizualised by epifluorescence microscopy and quantified by high-resolution liquid chromatography with a DAD-UV/Vis detector. Considering all five species and all the treatments, the oleic acid was the most catabolised. After priming, we identified two patterns in the fatty acid metabolism: (1) in non-chlorophyllous species, oleic, palmitic, and linoleic acids were catabolised during imbibition and (2) in crypto-chlorophyllous species, these fatty acids increased in concentration. These patterns suggest that crypto-chlorophyllous spores with homoiochlorophylly (chlorophyll retained after drying) might not require the assembly of new photosynthetic apparatus during dark imbibition. Thus, these spores might require less energy from pre-existing lipids and less fatty acids as 'building blocks' for cell membranes than non-chlorophyllous spores, which require de novo synthesis and structuring of the photosynthetic apparatus.