Molecular mechanisms and hormonal regulation underpinning morphological dormancy: a case study using Apium graveolens (Apiaceae)

Abstract

Underdeveloped (small) embryos embedded in abundant endosperm tissue, and thus having morphological dormancy (MD) or morphophysiological dormancy (MPD), are considered to be the ancestral state in seed dormancy evolution. This trait is retained in the Apiaceae family, which provides excellent model systems for investigating the underpinning mechanisms. We investigated Apium graveolens (celery) MD by combined innovative imaging and embryo growth assays with the quantification of hormone metabolism, as well as the analysis of hormone and cell-wall related gene expression. The integrated experimental results demonstrated that embryo growth occurred inside imbibed celery fruits in association with endosperm degradation, and that a critical embryo size was required for radicle emergence. The regulation of these processes depends on gene expression leading to gibberellin and indole-3-acetic acid (IAA) production by the embryo and on crosstalk between the fruit compartments. ABA degradation associated with distinct spatiotemporal patterns in ABA sensitivity control embryo growth, endosperm breakdown and radicle emergence. This complex interaction between gibberellins, IAA and ABA metabolism, and changes in the tissuespecific sensitivities to these hormones is distinct from non-MD seeds. We conclude that the embryo growth to reach the critical size and the associated endosperm breakdown inside MD fruits constitute a unique germination programme.

Transcriptome and Metabolite Conjoint Analysis Reveals the Seed Dormancy Release Process in Callery Pear

“…In addition, the absolute ABA content was much higher than the absolute GA3 content and the ABA/GA3 ratio showed a similar trend to ABA content (Figure 1B-E). These findings are consistent with those in the seeds of red bayberry [29], celery [30], and ginkgo [31]. Simultaneously, the expression patterns of several ABA and GA biosynthesis and deactivation genes, including SDRs, CYP707As, KO, KAO, and GA20oxs, exhibited high correlations with the changes in ABA and GA3 levels (Figure 4A).…”

Integrating Transcriptomics and Hormones Dynamics Reveal Seed Germination and Emergence Process in Polygonatum cyrtonema Hua

“…ABA levels are closely related to seed dormancy status. In this study, ABA levels showed a significant decline during the germination process ( Figure 2 ), which was similar to that of red bayberry [ 15 ], celery [ 16 ], ginkgo [ 17 ], and pear [ 18 ]. Concomitantly, the expression profiles of multiple ABA biosynthesis and deactivation genes, including NCEDs and CYP707As, were highly consistent with the dynamics of ABA ( Figure 2 ).…”

ABA and Bud Dormancy in Perennials: Current Knowledge and Future Perspective

“…Dormancy is an evolved trait of perennial plants that allows vegetative buds to survive harsh environmental conditions, and it was classified into three categories by Lang (1987): ecodormancy, caused by limitations in environmental factors; endodormancy, where the inhibition resides in the dormant structure itself, and paradormancy, inhibited by distal organs. Abscisic acid (ABA) is recognized as an essential phytohormone in dormancy regulation, especially as a central hub in seed dormancy [1][2][3][4], but its regulatory mechanism in bud dormancy is not well understood.…”