Comprehensive morphological and molecular analyses of flowering events in Bambusa tulda

Abstract

Flowering is one of the most important adaptations in the history of plant evolution. Our current understanding of flowering and the genes involved in the regulation of flowering time are based on the studies conducted on the model plants Arabidopsis thaliana and Oryza sativa. Since both these plants are annual and herbaceous, it is unlikely that the information obtained from these studies can directly be translated to explain the unusually extended flowering time in bamboo. The ecological impacts caused due to bamboo flowering are known for decades, but our knowledge about flower development and also the genes controlling such unique flowering behaviour is very inadequate in bamboo. a major objective of this study was to understand the detailed reproductive features of B. tulda Roxb. by studying the morphological (inflorescence, flower and pollen), histological (inflorescence) and biochemical (pollen viability) analyses. This study observed that protrandry, limited pollen liberation, low pollen viability and low seed setting are prevalent in B. tulda. Another major objective of this study was to characterize important flower induction and pathway integrator genes in order to understand their role in flower induction in tropical bamboos. Four copies of FLOWERING LOCUS T (BtFT1, BtFT2, BtFT3 and BtFT4) and two copies of FD (BtFD1, BtFD2) genes were identified and their tissue-specific as well as diurnal gene expression analyses revealed possible functional divergence among the closely related homologs. Taken together, this study indicates that copy number expansion and expression divergence may lead to new regulation of flowering gene functions in bamboo.