The phylotranscriptomic profile of angiosperm seed development follows a reverse hourglass pattern

Area of Science:

• Plant biology
• Developmental biology
• Evolutionary biology

Background:

• The angiosperm seed life cycle involves embryogenesis, maturation, and germination.
• Seed maturation is crucial for nutrient accumulation and desiccation tolerance.
• Previous studies indicated an hourglass pattern in embryogenesis and germination transcriptomes.

Purpose of the Study:

• To explore the transcriptomic landscape of the complete seed life cycle, focusing on seed maturation.
• To investigate phylotranscriptomic patterns during seed development in Arabidopsis thaliana and other species.

Main Methods:

• Utilized publicly available RNA-seq data.
• Generated transcriptome age index and transcriptome divergence index profiles.
• Conducted tissue-specific analyses in monocots.

Main Results:

• Revealed a reverse hourglass-like phylotranscriptome pattern across the seed life cycle.
• Seed maturation showed increased expression of younger, divergent genes compared to embryogenesis and germination.
• This pattern was conserved across dicots and monocots, with endosperm showing younger gene expression in monocots during maturation.

Conclusions:

• Seed maturation, like pollen development, is a key phase for expressing young, rapidly evolving genes.
• Propose the "out of the seed" hypothesis: seed maturation facilitates the expression of new genes and functional specialization.
• The findings offer insights into the evolution of plant reproductive strategies.