Mechanism Underlying The Involvement Of The Sorghum SbAGL6Gene Inarabidopsis Floral Transition

Sorghum, also named Shushu or Lusu in China, is an annual genus of gramine ous cropswith drought and water logging resistance, originally from Africa and suitable to grow inmoderate temperature conditions. Depending on the application purposes, this crop can beclassified as forage sorghum, food sorghum, sugar sorghum and broom sorghum. Sorghumseedlings are similar to those of corn, but they need to be air dried for forage use due to thetoxicity of the fresh stems and leaves. Sorghum is a short-day crop, so photoperiod is one ofthe key factors affecting its flowering time. In addition, some environmental factors such astemperature, humidity and endogenous signals also influence its floral transition. The studieson flowering time is of great significance for sorghum breeding, but the regulation mechanismof sorghum flowering induction remains largely unkown, which adversely affects the geneticimprovement of sorghum. The objectives of this study are to clarify the biological functionsof SbAGL6and to lay a foundation for revealing the molecular mechanisms underlying theflowering control in sorghum.In order to study the roles of SbAGL6gene in sorghum(Sorghum bicolor L.Moench), wecarried out RT-PCR to determine the expression patterns of SbAGL6gene in roots, stems,leaves, flowers and leaf sheaths from sorghum. Results showed that the SbAGL6geneaccumulated in the inflorescence of sorghum, but was not detected in the vegetative organs,such as roots, leaves, stems and leaf sheaths. To confirm PCR results, spikelet organs indifferent developmental stages were analyzed by in situ hybridization using SbAGL6RNAprobes. The results demonstrated that SbAGL6gene expressed and gradually enhanced duringthe transition of the apical leaf primordia to spikelet primodia, indicating that SbAGL6genemight participate in the process of floral organ formation.Transgenic Arabidopsis plants overexpressing SbAGL6gene after spraying DEX flowermuch earlier compared with wild type plants, confirming SbAGL6plays roles in theregulation of flowering time. In addition, overexpression of SbAGL6gene in transgenic plantsdid not induce homeotic phenotype in sepal, petal, pistil and stamen, indicating SbAGL6might not involve in the development of the floral organs. To provide deep insight intomolecular mechanism of SbAGL6functions, expressions of key genes controlling the floraltransition were measured in SbAGL6expressed Arabidopsis plants. The results showed thatSOC1and LFY genes, controlling floral transition and floral meristem functions, respectively, were activated, then flower specific genes AG and SEP1also were induced for early floweringinArabidopsis plants overexpressing SbAGL6.