Hormones regulate the flowering process in saffron differently depending on the developmental stage

Abstract

Flowering in saffron is a highly complex process regulated by the synchronized action of environmental cues and endogenous signals. Hormonal regulation of flowering is a very important process controlling flowering in several plants, but it has not been studied in saffron. Flowering in saffron is a continual process completed in months with distinct developmental phases, mainly divided into flowering induction and flower organogenesis/formation. In the present study, we investigated how phytohormones affect the flowering process at different developmental stages. The results suggest that different hormones differentially affect flower induction and formation in saffron. The exogenous treatment of flowering competent corms with abscisic acid (ABA) suppressed both floral induction and flower formation, whereas some other hormones, like auxins (indole acetic acid, IAA) and gibberellic acid (GA), behaved contrarily at different developmental stages. IAA promoted flower induction, while GA suppressed it; however, GA promoted flower formation, whereas IAA suppressed it. Cytokinin (kinetin) treatment suggested its positive involvement in flower induction and flower formation. The expression analysis of floral integrator and homeotic genes suggests that ABA might suppress floral induction by suppressing the expression of the floral promoter (LFY, FT3) and promoting the expression of the floral repressor (SVP) gene. Additionally, ABA treatment also suppressed the expression of the floral homeotic genes responsible for flower formation. GA reduces the expression of flowering induction gene LFY, while IAA treatment upregulated its expression. In addition to these genes, a flowering repressor gene, TFL1-2, was also found to be downregulated in IAA treatment. Cytokinin promotes flowering induction by increasing the expression levels of the LFY gene and decreasing the TFL1-2 gene expression. Moreover, it improved flower organogenesis by increasing the expression of floral homeotic genes. Overall, the results suggest that hormones differently regulate flowering in saffron via regulating floral integrator and homeotic gene expression.

A gibberellin-assisted study of the transcriptional and hormonal changes occurring at floral transition in peach buds (Prunus persica L. Batsch)

“…The analysis of DEGs related to bud development pointed out that response to auxin is upregulated at T1 and this is consistent with previous results showing a positive role of this hormone in flowering promotion in several species, among which Arabidopsis [ 82 , 83 ], strawberry [ 84 ], and saffron [ 85 ]. The contrast T3 vs. T5 revealed a generally increasing metabolic activity in terms of polysaccharide and cell wall organization, as well as an enhanced transcriptional activity, which are typical of an actively developing reproductive bud [ 86 – 88 ].…”

Health risk assessment of heavy metals in saffron (Crocus sativus L.) cultivated in domestic wastewater and lake water irrigated soils

“…Similarly, the flowering interval was significantly reduced ( p < 0.05) by 13.3–22.4%. Such earliness can be explained by the possible promotion of certain hormones (mostly IAA) responsible for flowering induction in saffron plants [ 76 ]. Higher organic matter and nutrient contents in soil can also play a crucial role in hastening the flowering period [ 77 ].…”

Transcriptional dynamics in source‐sink tissues identifies molecular factors regulating the corm development process in saffron (Crocus sativus L.)

“…In potatoes, StCEN is expressed mainly in leaves, whereas its expression was specific to corm in saffron, suggesting it has another role, unlike StCEN, probably in dormancy establishment. On the contrary, APETALA3‐like , which is involved in flower development in saffron (Singh et al 2023), was downregulated. The antagonistic expression of flowering repressor and integrator genes in corm tissue suggests that these genes are involved in maintaining the vegetative phase via suppression of reproductive meristem.…”