GA3 is superior to GA4 in promoting bud endodormancy release in tree peony (Paeonia suffruticosa) and their potential working mechanism

Abstract

Background Sufficient low temperature accumulation is the key strategy to break bud dormancy and promote subsequent flowering in tree peony anti-season culturing production. Exogenous gibberellins (GAs) could partially replace chilling to accelerate dormancy release, and different kinds of GAs showed inconsistent effects in various plants. To understand the effects of exogenous GA3 and GA4 on dormancy release and subsequent growth, the morphological changes were observed after exogenous GAs applications, the differentially expressed genes (DEGs) were identified, and the contents of endogenous phytohormones, starch and sugar were measured, respectively. Results Morphological observation and photosynthesis measurements indicated that both GA3 and GA4 applications accelerated bud dormancy release, but GA3 feeding induced faster bud burst, higher shoot and more flowers per plant. Full-length transcriptome of dormant bud was used as the reference genome. Totally 124 110 459, 124 015 148 and 126 239 836 reads by illumina transcriptome sequencing were obtained in mock, GA3 and GA4 groups, respectively. Compared with the mock, there were 879 DEGs and 2 595 DEGs in GA3 and GA4 group, 1 179 DEGs in GA3 vs GA4, and 849 DEGs were common in these comparison groups. The significant enrichment KEGG pathways of 849 DEGs highlighted plant hormone signal transduction, starch and sucrose metabolism, cell cycle, DNA replication, etc. Interestingly, the contents of endogenous GA1, GA3, GA4, GA7 and IAA significantly increased, ABA decreased after GA3 and GA4 treatments by LC–MS/MS. Additionally, the soluble glucose, fructose and trehalose increased after exogenous GAs applications. Compared to GA4 treatment, GA3 induced higher GA1, GA3 and IAA level, more starch degradation to generate more monosaccharide for use, and promoted cell cycle and photosynthesis. Higher expression levels of dormancy-related genes, TFL, FT, EBB1, EBB3 and CYCD, and lower of SVP by GA3 treatment implied more efficiency of GA3. Conclusions Exogenous GA3 and GA4 significantly accelerated bud dormancy release and subsequent growth by increasing the contents of endogenous bioactive GAs, IAA, and soluble glucose such as fructose and trehalose, and accelerated cell cycle process, accompanied by decreasing ABA contents. GA3 was superior to GA4 in tree peony forcing culture, which might because tree peony was more sensitive to GA3 than GA4, and GA3 had a more effective ability to induce cell division and starch hydrolysis. These results provided the value data for understanding the mechanism of dormancy release in tree peony.

Plant Development and Crop Yield: The Role of Gibberellins

“…The application of exogenous GA 3 to induce tree peony reflowering inhibits GA2ox , together with ZIP and NCED , and at the same time promotes the expression of ent -copalyl diphosphate synthase ( CPS ). Upregulation of CPS increases endogenous GA 3 level and reduces ABA content, suggesting that changes in ABA/GA balance allow bud dormancy release and reflowering in autumn [ 136 , 137 ].…”

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

“…Meanwhile, soluble sugars (glucose, sucrose, fructose, trehalose, etc.) increase during the transition from endodormancy to ecodormancy in buds of species such as leafy spurge, lily, sweet cherry and tree peony [26,65,[69][70][71]. At the bud dormancy induction stage, sucrose in parenchyma cells declines and Tre6P (Trehalose 6-phosphate) decreases, which activates SnRK1 activity and stimulates ABA biosynthesis [72].…”

“…The effect of GA on bud dormancy is dependent on spatio-temporal and species' variety [29,71,90]. In most cases, GA has a positive role in bud endodormancy release.…”

Regulation of the Bud Dormancy Development and Release in Micropropagated Rhubarb ‘Malinowy’

“…The enhanced expression of GAMYB in rhubarb buds during dormancy release might suggest the GA-promoted production of α-amylases. Generally, the balance between ABA and GA significantly influences dormancy regulation [51][52][53]. These results indicated that the decreased expression of ABA precursor (ZEP) and increased levels of ABF2 involved in ABA signal transduction and metabolism were consistent with the reduced levels of ABA in the rhubarb buds during dormancy release.…”