Overexpression of Larch SCL6 Inhibits Transitions from Vegetative Meristem to Inflorescence and Flower Meristem in Arabidopsis thaliana (L.) Heynh.

SCARECROW-LIKE6 (SCL6) plays a role in the formation and maintenance of the meristem. In Larix kaempferi (Lamb.) Carr., an important afforestation tree species in China, SCL6 (LaSCL6) has two alternative splicing variants-LaSCL6-var1 and LaSCL6-var2-which are regulated by microRNA171. However, their roles are still unclear. In this study, LaSCL6-var1 and LaSCL6-var2 were transformed into the Arabidopsis thaliana (L.) Heynh. genome, and the phenotypic characteristics of transgenic A. thaliana, including the germination percentage, root length, bolting time, flower and silique formation times, inflorescence axis length, and branch and silique numbers, were analyzed to reveal their functions. It was found that LaSCL6-var1 and LaSCL6-var2 overexpression shortened the root length by 41% and 31%, respectively, and increased the inflorescence axis length. Compared with the wild type, the bolting time in transgenic plants was delayed by approximately 2-3 days, the first flower and silique formation times were delayed by approximately 3-4 days, and the last flower and silique formation times were delayed by about 5 days. Overall, the life cycle in transgenic plants was prolonged by approximately 5 days. These results show that LaSCL6 overexpression inhibited the transitions from the vegetative meristem to inflorescence meristem and from the flower meristem to meristem arrest in A. thaliana, revealing the roles of LaSCL6-var1 and LaSCL6-var2 in the fate transition and maintenance of the meristem.