Comparative Transcriptome Analysis Provides Insight into the Effect of 6-BA on Flower Development and Flowering in <i>Bougainvillea</i>

Abstract

Bougainvillea spp. is a well-known ornamental plant that is widely applied in urban landscaping construction. The colorful bracts of Bougainvillea in full bloom become important for urban landscape during special festivals. Although flowering regulation measures of Bougainvillea attracted much attention, the underlying mechanism of flower bud differentiation and development remains poorly understood. Here, we induced flowering of Bougainvillea glabra ‘Sao Paulo’ under 6-BA treatment and conducted RNA sequencing data analysis to characterize the molecular regulatory mechanism of flower development in response to 6-BA. Transcriptome analysis indicated that a series of genes and transcription factors of cytokinin metabolism, flowering and floral development regulation, and photoperiod regulation were upregulated by the 6-BA treatment, including COL, AP2, FT, SOC1, LFY, SPL4, SPL9, and SPL13. Moreover, the expression of these important genes exhibited relatively high levels of thorns compared to apical buds, suggesting that flower bud differentiation probably starts with the thorns in Bougainvillea. This study confirms that 6-BA treatment at certain concentrations can promote flowering of Bougainvillea and provides insight into the regulatory mechanism of the growth regulator acting on early flowering of Bougainvillea.</i