A petunia transcription factor, PhOBF1, regulates flower senescence by modulating gibberellin biosynthesis

A tree peony RING-H2 finger protein, PsATL33, plays an essential role in cold-induced bud dormancy release by regulating gibberellin content

Bud dormancy is crucial for woody perennial plants to resist low-temperature stress in winter. However, the molecular regulatory mechanisms underlying bud dormancy release are largely unclear. Here, a tree peony (Paeonia suffruticosa) transcript ARABIDOPSIS TOXICOS EN LEVADURA 33 (PsATL33), encoding a RING-H2 finger protein, was selected from previously generated RNA sequencing data of chilling-treated buds. The objective of this study is to investigate the role of PsATL33 in the regulation of cold-induced bud dormancy release. Subcellular localization assay revealed that PsATL33 was localized to the nucleus and plasma membrane. Reverse transcription-quantitative PCR analysis showed that PsATL33 was dramatically upregulated during cold-triggered bud dormancy release. Exogenous treatments with gibberellin (GA3) increased, but abscisic acid (ABA) inhibited the transcription of PsATL33. Ectopic transformation assay indicated that overexpression of PsATL33 in petunia promoted seed germination, plant growth, and axillary bud break. Silencing of PsATL33 in tree peony through virus-induced gene silencing assay delayed bud dormancy release. tobacco rattle virus (TRV)-PsATL33-infected buds exhibited reduced expression levels of dormancy break-related genes EARLY BUD-BREAK 1 (PsEBB1) and CARBOXYLESTERASE 15 (PsCXE15). Silencing of PsATL33 decreased the accumulation of bioactive GAs, GA1 and GA3, rather than ABA. Transcript levels of several genes involved in GA biosynthesis and signaling, including GA20-OXIDASE 1 (PsGA20ox1), GA3-OXIDASE 1 (PsGA3ox1), PsGA3ox3, GA2-OXIDASE 1 (PsGA2ox1), and GA-INSENSITIVE 1A (PsGAI1A), were changed by PsATL33 silencing. Taken together, our data suggest that PsATL33 functions as a positive regulator of cold-induced bud dormancy release by modulating GA production.

Abscisic acid-induced transcription factor PsMYB306 negatively regulates tree peony bud dormancy release

Bud dormancy is a crucial strategy for perennial plants to withstand adverse winter conditions. However, the regulatory mechanism of bud dormancy in tree peony (Paeonia suffruticosa) remains largely unknown. Here, we observed dramatically reduced and increased accumulation of abscisic acid (ABA) and bioactive gibberellins (GAs) GA1 and GA3, respectively, during bud endodormancy release of tree peony under prolonged chilling treatment. An Illumina RNA sequencing study was performed to identify potential genes involved in the bud endodormancy regulation in tree peony. Correlation matrix, principal component, and interaction network analyses identified a downregulated MYB transcription factor gene, PsMYB306, the expression of which positively correlated with 9-CIS-EPOXYCAROTENOID DIOXYGENASE 3 (PsNCED3) expression. Protein modeling analysis revealed 4 residues within the R2R3 domain of PsMYB306 to possess DNA binding capability. Transcription of PsMYB306 was increased by ABA treatment. Overexpression of PsMYB306 in petunia (Petunia hybrida) inhibited seed germination and plant growth, concomitant with elevated ABA and decreased GA contents. Silencing of PsMYB306 accelerated cold-triggered tree peony bud burst and influenced the production of ABA and GAs and the expression of their biosynthetic genes. ABA application reduced bud dormancy release and transcription of ENT-KAURENOIC ACID OXIDASE 1 (PsKAO1), GA20-OXIDASE 1 (PsGA20ox1), and GA3-OXIDASE 1 (PsGA3ox1) associated with GA biosynthesis in PsMYB306-silenced buds. In vivo and in vitro binding assays confirmed that PsMYB306 specifically transactivated the promoter of PsNCED3. Silencing of PsNCED3 also promoted bud break and growth. Altogether, our findings suggest that PsMYB306 negatively modulates cold-induced bud endodormancy release by regulating ABA production.

Investigation of Volatile Components and Assessment of Antioxidant Potential in Seven Lamiaceae Plant Hydrosols

Aromatic plants of the family Lamiaceae, especially of the genus Thymus, have promising antioxidant applications in pharmacology, medicine, food, cosmetology, and aromatherapy. Hydrosols (HDs) were extracted by hydrodistillation from seven species of Lamiaceae, including Thymus vulgaris, Thymus mongolicus, Mentha × piperita, Melissa officinalis, Rosmarinus officinali, Salvia elegans, and Leonurus artemisia. In total, 369 volatile components were determined and analyzed by gas chromatography-mass spectrometry (GC-MS). Among them, alcohols (2.86-28.48%), ethers (2.46-10.69%), and phenols (0.11-21.78%) constituted a large proportion, mainly linalool (0.28-19.27%), eucalyptol (0.16-6.97%), thymol (0-19.54%), and carvacrol (0-26.82%). Multivariate statistical analyses were performed and 27 differential metabolites were screened. Three different methods (ABTS+•, DPPH•, and FRAP) were used to determine the in vitro antioxidant activity of seven HDs. Thymus vulgaris hydrosols (Tv HDs) and Thymus mongolicus hydrosols (Tm HDs) had the strongest antioxidant activity and their stronger antioxidant capacity was related to their high levels of phenolic constituents, mainly thymol. The antioxidant activity of the other five Lamiaceae HDs was associated with their high alcohol (mainly linalool and eucalyptol) content, and the alcohol constituents may synergistically affect their antioxidant capacity. Therefore, the present study suggests that Lamiaceae plants can be utilized as antioxidant products or antioxidants in different industrial sectors including pharmaceuticals, food, cosmetics, and agrochemicals.