Seed germination and dormancy: The classic story, new puzzles, and evolution

Abstract

This review highlights recent progresses in seed germination and dormancy research. Research on the weakening of the endosperm during germination, which is almost a classic theme in seed biology, was resumed by α‐xylosidase studies. Strong genetic evidence was presented to suggest that the quality control of xyloglucan biosynthesis in the endosperm (and the embryo) plays a critical role in germination. Further analyses on the endosperm and the adjacent layers have suggested that the cutin coat in the endosperm‐testa interphase negatively affects germination while the endosperm‐embryo interphase produces a sheath that facilitates germination. These progresses significantly advanced our understanding of seed germination mechanisms. A breakthrough in dormancy research, on the other hand, revealed the unique abscisic acid signaling pathway that is regulated by DELAY OF GERMINATION1 (DOG1). The detailed analysis of DOG1 expression uncovered the intriguing story of reciprocal regulation of the sense‐antisense pair, which generated new questions. Recent studies also suggested that the DOG1 function is not limited to dormancy but extended through general seed maturation, which provokes questions about the evolution of DOG1 family proteins. Seed biology is becoming more exciting with the classic stories being revitalized and new puzzles emerging from the frontier.

Network Analysis Prioritizes DEWAX and ICE1 as the Candidate Genes for Major eQTL Hotspots in Seed Germination

“…Although the function of this gene has never been reported in seeds, the presence of a cuticular layer indeed plays 222 a significant role in maintaining seed dormancy (De Giorgi et al, 2015;Nonogaki, 2019). In Arabidopsis seeds, 223 the thick cuticular structure covering the endosperm prevents cell expansion and testa rupture that precede radicle 224 protrusion.…”

Delay of Germination-1 (DOG1): A Key to Understanding Seed Dormancy

“…Together, current data indicate that DOG1 function is not strictly limited to PD process, but that it is also required for other facets of seed maturation, in part by also interfering with the ethylene signaling components. Otherwise, since DOG1 also affects other processes such us flowering and drought tolerance, the approaches to understanding its mechanism of action and control are, at this time, still inconclusive.Plants 2020, 9, 480 2 of 20 (e.g., temperature, O 2 and light) [1][2][3][4]. PD dormancy is a notable agronomic feature.…”

“…Thus, low levels may produce pre-harvest sprouting, while high levels inhibit the rapid and uniform germination rate. In both cases, there is a reduction of crop production [1,4,5]. PD is established and maintained in the viable dry seed, and throughout several molecular paths (e.g., after-ripening (AR) and exposure to gentle cooling) and can be broken gradually [6,7].…”

“…PD is established and maintained in the viable dry seed, and throughout several molecular paths (e.g., after-ripening (AR) and exposure to gentle cooling) and can be broken gradually [6,7]. On the other hand, non-dormant seeds of various species have been reported to achieve secondary dormancy (SD) upon exposure to unfavorable conditions for germination [1]. SD occurs essentially after seed dispersal and may be induced by environmental interactions or other special conditions.…”

“…The first four DOGL genes are located on chromosome 4 next to each other, while DOGL5 was found on chromosome 3. The DOG1 family in Arabidopsis has several conserved domains whose functions are still under study [1,5]. DOGL1, DOGL2, and DOGL3 are relatively like DOG1, whereas DOGL4 and DOGL5 show only 28 and 30% similarity with DOG1 in amino acid sequence, respectively [1].…”