Isolation and Functional Characterization of the MADS-Box Gene AGAMOUS-LIKE 24 in Rubber Dandelion (Taraxacum...

Rubber dandelion (Taraxacum kok-saghyz Rodin, TKS), also referred to as Russian dandelion, is one of the most promising natural rubber (NR)-producing plants that produce high-quality NR comparable to that from the Pará rubber tree (Hevea brasiliensis, Hb), currently the only commercial source. It needs further breeding to improve the agricultural traits. However, little has been known about the genetic mechanisms underlying the regulation of floral induction and flower development in TKS, an important trait that remains to be improved for commercial production. The MADS-box gene AGAMOUS-LIKE 24 (AGL24) plays important roles in floral induction and flower development. As the first step in understanding its roles in TKS, this study isolated and characterized the AGL24-homologous gene TkAGL24 in TKS. The TkAGL24 gene had a 705 bp coding sequence (CDS) that encoded a protein of 234 amino acids containing the conserved classic MADS-box type II domain and K-box domain, sharing 55.32% protein sequence identity with the AtAGL24 protein from Arabidopsis. TkAGL24 was highly expressed in leaf, latex, root, and peduncle but rarely or not in mature flower. The TkAGL24 protein was located in the nucleus and cytoplasm and did not have transcription activation activity in yeast cells. The overexpression of TkAGL24 in Arabidopsis could promote flowering and cause the abnormal development of flowers, similar to other AGL24-homologous genes from other species. Furthermore, the overexpression of TkAGL24 in TKS also affected the development of ligulate flowers. These results suggested that the cloned TkAGL24 gene is functional and may play important roles in floral induction and flower development in TKS, providing an insight into the possibility for the further studies of its roles and application to breeding.