The phytomelatonin receptor PMTR1 regulates seed development and germination by modulating abscisic acid homeostasis in Arabidopsis thaliana

Abstract

Melatonin is known to involve multiple physiological actions in plants. Herein, we found that exogenous melatonin inhibited the Arabidopsis seedling growth through the elevated abscisic acid (ABA) levels, and the elevated ABA was ascribed to the upregulation of 9‐cis‐epoxycarotenoid dioxygenase genes (NCEDs) in the ABA biosynthesis pathway. We also found that the overexpression lines of the melatonin receptor gene PMTR1 (also known as Cand2) yielded smaller seeds and germinated slower than the wild type, whereas PMTR1‐knockout mutants produced larger seeds and germinated faster than the wild type. During the seed development, the accumulation peak of ABA was higher in the PMTR1‐knockout mutant, while it was lower in the PMTR1‐overexpression line than that in the wild type. In the dry seeds and imbibed seeds, the PMTR1‐overexpression line accumulated higher ABA levels, while the PMTR1‐knockout contained less ABA than the wild type. In summary, our findings suggest that PMTR1 is involved in ABA‐mediated seed development and germination in Arabidopsis.

Phytomelatonin: an emerging new hormone in plants

“…Several studies have found that melatonin can promote seed germination under stress conditions, especially in old or damaged seeds, improving germination rate probably through fit hormonal balance ( K. Wang et al , 2022 ). In contrast, Lv et al (2021) and Yin et al (2022) have shown that high concentrations of melatonin inhibit Arabidopsis seed germination and seedling growth, possibly due to disorder in ABA, GA, and auxin balance. It is interesting that PMTR1 -knockout mutants contain higher ABA concentrations in developing seeds, but accumulate lower ABA contents in dry and imbibed seeds than the wild-type Col-0 ( Yin et al , 2022 ), indicating that PMTR1 is involved in phytomelatonin-mediated seed development, dormancy, germination, and seedling growth via crosstalk with ABA signaling.…”

“…In contrast, Lv et al (2021) and Yin et al (2022) have shown that high concentrations of melatonin inhibit Arabidopsis seed germination and seedling growth, possibly due to disorder in ABA, GA, and auxin balance. It is interesting that PMTR1 -knockout mutants contain higher ABA concentrations in developing seeds, but accumulate lower ABA contents in dry and imbibed seeds than the wild-type Col-0 ( Yin et al , 2022 ), indicating that PMTR1 is involved in phytomelatonin-mediated seed development, dormancy, germination, and seedling growth via crosstalk with ABA signaling. Transgenic Arabidopsis plants overexpressing AtPMTR1 produce smaller seeds and germinate more slowly than Col-0 plants ( Yin et al , 2022 ).…”

“…GA and strigolactone), ROS signaling, and the central components of floral-gene regulation networks ( Chen et al , 2022 ). CRISPR/cas9-edited plants and overexpressing lines of PMTR1 show earlier and later flowering, respectively, than Arabidopsis wild-type Col-0 ( Yin et al , 2022 ), indicating the phytomelatonin-mediated delay of flowering time is likely to be dependent on the PMTR1 receptor.…”

“…It is interesting that PMTR1 -knockout mutants contain higher ABA concentrations in developing seeds, but accumulate lower ABA contents in dry and imbibed seeds than the wild-type Col-0 ( Yin et al , 2022 ), indicating that PMTR1 is involved in phytomelatonin-mediated seed development, dormancy, germination, and seedling growth via crosstalk with ABA signaling. Transgenic Arabidopsis plants overexpressing AtPMTR1 produce smaller seeds and germinate more slowly than Col-0 plants ( Yin et al , 2022 ). The application of melatonin can induce seedless fruits of pear via regulation of GA pathways ( Liu et al , 2018 ).…”

Herbaceous peony AP2/ERF transcription factor binds the promoter of the tryptophan decarboxylase gene to enhance high‐temperature stress tolerance

“…Melatonin ( N ‐acetyl‐5‐methoxytryptamine) is an endogenous micromolecular indoleamine compound that has multiple physiological functions in various organisms (Zhang & Zhang, 2021), and the identification of phytomelatonin receptor 1 (PMTR1) has been a turning point for understanding phytomelatonin functions (Wang et al, 2021; Wei et al, 2018; Yin et al, 2022). Phytomelatonin not only plays an important role in regulating plant growth and development (Arnao & Hernández‐Ruiz, 2020; Li et al, 2022) but is also a well‐known antioxidant that improves plant tolerance to various abiotic stresses (Arnao & Hernández‐Ruiz, 2019; Zhang et al, 2019).…”