Characterization of JsWOX1 and JsWOX4 during Callus and Root Induction in the Shrub Species Jasminum sambac

Plant regeneration in vitro and the underlying molecular regulatory network are of great interest to developmental biology, and have potential applications in agriculture and biotechnology. Cell growth and re-differentiation during de novo organogenesis require the activation and reprogramming of stem cells within the stem cell niche of the tissues. The WUSCHEL-related homeobox (WOX) factors play important roles in the maintenance and regulation of plant stem cells and are involved in many developmental processes. However, in woody species such as the Jasminum sambac, little is known about the involvement of WOX genes in de novo organogenesis. Here we show that two WOXs, JsWOX4 and JsWOX1, are implicated in callus proliferation and root regeneration, respectively. The expression of both, together with another member JsWOX13, are upregulated during later stage of callus formation. The JsWOX4 is associated with callus proliferation, or cell division during the redifferentiation. The overexpression of this gene results in up-regulation of JsWOX13 and another homeobox gene. The JsWOX1 plays a role in root primordium initiation, as its overexpression leads to more rooty calli and more roots per callus. JsWOX1 also possibly acts upstream of JsWOX4 and JsWOX13 transcriptionally. Our results provide further evidence regarding the functions of WOX genes in organogenesis in a woody plant.