Molecular cloning, expression analyses and primary evolution studies of REV- and TB1-like genes in bamboo

Most cultured bamboos are perennial woody evergreens that reproduce from rhizomes. It is unclear why some rhizome buds develop into aerial bamboo shoots instead of new rhizomes. REVOLUTA (REV)-like Class III homeodomain leucine-zipper (HD-Zip) proteins and TEOSINTE BRANCHED1 (TB1)-like transcription factors have been shown to play regulatory roles in meristem initiation and outgrowth. We cloned and analyzed the bamboo (Phyllostachys praecox C.D. Chu & C.S. Chao.) REV- (PpHB1) and TB1-like (PpTB1) gene. Gene expression was mainly detected by in situ hybridization. PpHB1 expression was detected in the tips of lateral buds, on the adaxial portion of the leaf and within the developing procambium, indicating its close correlation to rhizome bud formation and procambial development. PpTB1 expression was mainly detected on the top of buds at later developmental stages, suggesting it was more likely involved in bud outgrowth. Meristem genes might therefore serve as specific molecular markers of rhizome bud development and could be useful in studies designed to elucidate the mechanisms underlying bamboo shoot development. In addition, meristem genes such as TB1-like sequences may be useful in phylogenetic analyses of bamboo species.