Most cited article - PubMed ID 37063214
Distinct hormonal and morphological control of dormancy and germination in Chenopodium album dimorphic seeds
Chenopodium ficifolium is a close diploid relative of the tetraploid crop Chenopodium quinoa. Owing to its reproducible germination and seedling development, it becomes a promising model for studying floral induction, providing a basis for the comparison with C. quinoa. Two C. ficifolium genotypes differ in photoperiodic requirement: C. ficifolium 283 accelerates flowering under long days, whereas C. ficifolium 459 flowers earlier under short days. This study conducted a comprehensive transcriptomic and hormonomic analysis of floral induction in the long-day C. ficifolium 283 and compared the findings to previous experiments with the short-day C. ficifolium. Phytohormone concentrations and gene expression profiles during floral induction were largely similar between the two genotypes. However, a subset of genes exhibited contrasting expression patterns, aligning with the genotypes' differing photoperiodic requirements. These genes, predominantly homologs of flowering-related genes in Arabidopsis thaliana, were activated under long days in C. ficifolium 283 and under short days in C. ficifolium 459. Notably, the contrasting expression of the FLOWERING LOCUS T-LIKE 2-1 gene, which was previously shown to induce precocious flowering in A. thaliana, confirmed its role as a floral activator, despite its low expression levels.
- Keywords
- Flowering, genes with contrasting expression trends, long-day Chenopodium ficifolium, phytohormones, transcriptome,
- MeSH
- Chenopodium * genetics MeSH
- Photoperiod MeSH
- Genotype MeSH
- Flowers * genetics growth & development MeSH
- Gene Expression Regulation, Plant * MeSH
- Plant Growth Regulators metabolism MeSH
- Genes, Plant MeSH
- Plant Proteins genetics metabolism MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Plant Growth Regulators MeSH
- Plant Proteins MeSH
Plants in habitats with unpredictable conditions often have diversified bet-hedging strategies that ensure fitness over a wider range of variable environmental factors. A striking example is the diaspore (seed and fruit) heteromorphism that evolved to maximize species survival in Aethionema arabicum (Brassicaceae) in which external and endogenous triggers allow the production of two distinct diaspores on the same plant. Using this dimorphic diaspore model, we identified contrasting molecular, biophysical, and ecophysiological mechanisms in the germination responses to different temperatures of the mucilaginous seeds (M+ seed morphs), the dispersed indehiscent fruits (IND fruit morphs), and the bare non-mucilaginous M- seeds obtained by pericarp (fruit coat) removal from IND fruits. Large-scale comparative transcriptome and hormone analyses of M+ seeds, IND fruits, and M- seeds provided comprehensive datasets for their distinct thermal responses. Morph-specific differences in co-expressed gene modules in seeds, as well as in seed and pericarp hormone contents, identified a role of the IND pericarp in imposing coat dormancy by generating hypoxia affecting abscisic acid (ABA) sensitivity. This involved expression of morph-specific transcription factors, hypoxia response, and cell wall remodeling genes, as well as altered ABA metabolism, transport, and signaling. Parental temperature affected ABA contents and ABA-related gene expression and altered IND pericarp biomechanical properties. Elucidating the molecular framework underlying the diaspore heteromorphism can provide insight into developmental responses to globally changing temperatures.
- MeSH
- Brassicaceae * genetics physiology metabolism MeSH
- Germination * genetics physiology MeSH
- Abscisic Acid metabolism MeSH
- Fruit * genetics physiology growth & development metabolism MeSH
- Gene Expression Regulation, Plant * MeSH
- Plant Growth Regulators metabolism MeSH
- Seeds * genetics physiology growth & development metabolism MeSH
- Temperature * MeSH
- Transcriptome genetics MeSH
- Plant Dormancy genetics physiology MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Abscisic Acid MeSH
- Plant Growth Regulators MeSH
The transition from germinating seeds to emerging seedlings is one of the most vulnerable plant life cycle stages. Heteromorphic diaspores (seed and fruit dispersal units) are an adaptive bet-hedging strategy to cope with spatiotemporally variable environments. While the roles and mechanisms of seedling traits have been studied in monomorphic species, which produce one type of diaspore, very little is known about seedlings in heteromorphic species. Using the dimorphic diaspore model Aethionema arabicum (Brassicaceae), we identified contrasting mechanisms in the germination responses to different temperatures of the mucilaginous seeds (M+ seed morphs), the dispersed indehiscent fruits (IND fruit morphs), and the bare non-mucilaginous M- seeds obtained from IND fruits by pericarp (fruit coat) removal. What follows the completion of germination is the pre-emergence seedling growth phase, which we investigated by comparative growth assays of early seedlings derived from the M+ seeds, bare M- seeds, and IND fruits. The dimorphic seedlings derived from M+ and M- seeds did not differ in their responses to ambient temperature and water potential. The phenotype of seedlings derived from IND fruits differed in that they had bent hypocotyls and their shoot and root growth was slower, but the biomechanical hypocotyl properties of 15-day-old seedlings did not differ between seedlings derived from germinated M+ seeds, M- seeds, or IND fruits. Comparison of the transcriptomes of the natural dimorphic diaspores, M+ seeds and IND fruits, identified 2,682 differentially expressed genes (DEGs) during late germination. During the subsequent 3 days of seedling pre-emergence growth, the number of DEGs was reduced 10-fold to 277 root DEGs and 16-fold to 164 shoot DEGs. Among the DEGs in early seedlings were hormonal regulators, in particular for auxin, ethylene, and gibberellins. Furthermore, DEGs were identified for water and ion transporters, nitrate transporter and assimilation enzymes, and cell wall remodeling protein genes encoding enzymes targeting xyloglucan and pectin. We conclude that the transcriptomes of seedlings derived from the dimorphic diaspores, M+ seeds and IND fruits, undergo transcriptional resetting during the post-germination pre-emergence growth transition phase from germinated diaspores to growing seedlings.
