Determination of growth stages and metabolic profiles in Brachypodium distachyon for comparison of developmental context with Triticeae crops

Abstract

Brachypodium distachyon is an emerging model plant for studying biological phenomena in temperate grasses. Study of the growth scale is essential to analyse spatio-temporal changes in molecular factors throughout the life cycle. For sensitive and robust staging based on morphology in B. distachyon, we demonstrated the utility of the BBCH (Biologische Bundesanstalt, Bundessortenamt and CHemical industry) scale, which is comparable to the Zadoks scale conventionally used for Triticeae crops. We compared the chronological progression of B. distachyon accessions Bd21 and Bd3-1, in addition to the progression of Chinese Spring wheat. The comparison of growth stages illustrates the morphological similarities and differences in the timing of life cycle events. Furthermore, we compared metabolite accumulation patterns across different growth stages and across different stress conditions using a widely targeted metabolome analysis. Metabolic profiling determined commonalities and specificities in chemical properties that were dependent on organisms, growth stages and/or stress conditions. Most metabolites accumulated equivalently in B. distachyon and wheat. This qualitative similarity indicated the superiority of B. distachyon as a model for Triticeae crops. The growth scale of B. distachyon should provide a conceptual framework for comparative analysis and for knowledge integration between this model grass and crops in the Pooideae subfamily.

Keywords: BBCH scale; Brachypodium distachyon; Pooideae; Zadoks scale; growth staging; metabolome.

Figure 1.

Chronological growth stages of the BBCH scale in Bd21, Bd3-1 and Chinese Spring wheat. Days between imbibition and each BBCH growth stage are indicated by horizontal bars (±s.d.). Red, blue and black markers represent Bd21, Bd3-1 and wheat, respectively, under a day length of 20 h.

Figure 2.

Flower structure and endosperm development. (a) Spikelet. (b) Floret. (c) Dehiscent anther and pollen grains. (d) Pollen grains attached to the stigma. (e) SEM image of the pollen surface structure. (f–j) Endosperm development towards BBCH71 (i) and BBCH73 (j). Scale bars: (a) 5 mm; (b) 1 mm; (c) 500 µm; (d) 200 µm; (e) 10 µm; (f–j) 1 mm.

Figure 3.

Metabolite profiling of the seeds and leaves of Bd21, Bd3-1 and Chinese Spring wheat at different growth stages. Dendrogram and heat map show metabolite accumulation, clustered based on the binary logarithm (log₂) values of quantitative data, which were obtained by UPLC-TQS. Only the first leaves were used as leaf samples.

Figure 4.

Metabolite profiling of the leaves of Bd21, Bd3-1 and Chinese Spring wheat under stress conditions. Dendrogram and heat map show metabolite accumulation, clustered based on the binary logarithm (log₂) value of quantitative data obtained by UPLC-TQS. Only the first leaves were used.