Oryza longistaminata, the African wild rice, can propagate vegetatively through rhizomes. Rhizomes elongate horizontally underground as sink organs, however, they undergo a developmental transition that shifts their growth to the surface of the ground to become aerial stems. This particular stage is essential for the establishment of new ramets. While several determinants such as abiotic stimuli and plant hormones have been reported as key factors effecting developmental transition in aerial stem, the cause of this phenomenon in rhizome remains elusive. This study shows that depletion of nutrients, particularly sucrose, is the key stimulus that induces the developmental transition in rhizomes, as indicated by the gradient of sugars from the base to the tip of the rhizome. Sugar treatments revealed that sucrose specifically represses the developmental transition from rhizome to aerial stem by inhibiting the expression of sugar metabolism and hormone synthesis genes at the bending point. Sucrose depletion affected several factors contributing to the developmental transition of rhizome including signal transduction, transcriptional regulation and plant hormone balance.
Keywords: Developmental transition; Gravitropism; Oryza longistaminata; Rhizome; Sucrose.