Abstract
Bamboos, member of the family Poaceae, represent many interesting features with respect to their fast and extended vegetative growth, unusual, yet divergent flowering time across species, and impact of sudden, large scale flowering on forest ecology. However, not many studies have been conducted at the molecular level to characterize important genes that regulate vegetative and flowering habit in bamboo. In this study, two bamboo FD genes, BtFD1 and BtFD2, which are members of the florigen activation complex (FAC) have been identified by sequence and phylogenetic analyses. Sequence comparisons identified one important amino acid, which was located in the DNA-binding basic region and was altered between BtFD1 and BtFD2 (Ala146 of BtFD1 vs. Leu100 of BtFD2). Electrophoretic mobility shift assay revealed that this alteration had resulted into ten times higher binding efficiency of BtFD1 than BtFD2 to its target ACGT motif present at the promoter of the APETALA1 gene. Expression analyses in different tissues and seasons indicated the involvement of BtFD1 in flower and vegetative development, while BtFD2 was very lowly expressed throughout all the tissues and conditions studied. Finally, a tenfold increase of the AtAP1 transcript level by p35S::BtFD1 Arabidopsis plants compared to wild type confirms a positively regulatory role of BtFD1 towards flowering. However, constitutive expression of BtFD1 had led to dwarfisms and apparent reduction in the length of flowering stalk and numbers of flowers/plant, whereas no visible phenotype was observed for BtFD2 overexpression. This signifies that timely expression of BtFD1 may be critical to perform its programmed developmental role in planta.
Highlights
Bamboos belong to the subfamily Bambusoideae, family Poaceae and are widely distributed in Asia, Africa and America[1,2]
To study the role and diversity of FD genes (Table 1) in bamboo, B. tulda was selected, because its floral developmental stages have relatively been better characterized than any other bamboo species[11,43], occurrence of sporadic flowering events in the species from time to time[4,44] and its enormous economic importance in Asia
Bamboo FD genes are similar to other Poaceae FD homologs in terms of sequence similarity and phylogenetic relationships
Summary
Bamboos belong to the subfamily Bambusoideae, family Poaceae and are widely distributed in Asia, Africa and America[1,2]. The loss-of-function mutation of either AtFD or AtFDP resulted in late flowering in Arabidopsis, while their overexpression demonstrated early flowering indicating their possible involvement in flowering[37,38]. In addition to flower induction, other pleiotropic roles of FD genes such as inflorescence development[39,40], leaf d evelopment[29] and alternative growth c essation[41,42] have been observed. This clearly indicates that FD performs diverse important roles in the vegetative and reproductive developments of plants
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