A flowering inhibitor of the temperature-dependent pathway in Crocus sativus L

Saffron is the world highest-priced spice because its production requires intensive hand labour. Reduce saffron production costs require containerised plant production under controlled conditions and expand the flowering period. Controlling the flowering process and identify the factors involved in saffron flowering is crucial to introduce technical improvements. The research carried out so far in saffron has allowed an extensive knowledge of the influence of temperature on the flower induction, but the molecular mechanisms controlling flowering induction processes are largely unknown. The present study is the first conducted to isolate and characterize a regulator gene of saffron floral induction the Short Vegetative Phase (SVP) gene, which represses the floral initiation genes in the temperature response pathway, which involved in saffron flower induction. The results obtained from both phylogenetic analysis and T-coffee alignment confirms that the isolated sequence belongs to the SVP gene clades of MADS-box gene family. Gene expression analysis in different developmental stages revealed the highest expression of SVP transcript (CsSVP) during the dormancy and the vegetative stages, but decrease when flower development initiated and it was the least in late September when flower primordia are developed. Furthermore, its expression increased in the apical bud when corms are storage at 9-10 ºC, thus inhibiting flower induction. Additionally, comparison of the CsSVP transcript in apical buds from big and small corms, differing in their flowering capacity, indicates that the CsSVP transcript is present only in vegetative buds. Taken together, these results suggested inhibitory role of the SVP gene.