Paclobutrazol induces changes in transcriptomic and endogenous hormone profiles in yellow camellia for reproductive phase transition

Abstract Yellow camellias, also known as golden camellias, are prized for their ornamental, medicinal, and edible values. Because common camellia flowers are either red, purple, pink, or white, golden flowers are rare and are in high market demand. In previous studies, we have demonstrated that paclobutrazol, a synthetic triazole-type cytochrome P450 growth inhibitor that inhibits gibberellins (GA) biosynthesis, is effective in inducing floral buds in juvenile yellow camellias. In this study, we conducted transcriptomics and endogenous phytohormone analyses with undifferentiated buds, vegetative buds, and floral buds (induced with paclobutrazol), with the aim of understanding how paclobutrazol induces vegetative to reproductive phase transition. RNA sequencing (RNA-seq) generated a total of 313,689,058 transcripts, revealing many floral genes for the first time in yellow camellia and providing a valuable genomic resource for future studies. Comparisons among different timepoints and between floral and vegetative buds generated a total of 10,944 DE transcript isoforms and 12,524 DE genes, with the majority of them being identified in the comparison between floral buds and undifferentiated buds. In floral buds, the GA and cytokinin levels significantly decreased, while the ABA level increased. The expression of genes controlling vegetative to reproductive phase transition, such as AG , SPL1 , CAL , and AP1 , was significantly enhanced. This might have led to the formation of floral buds in the paclobutrazol-treated juvenile yellow camellia.

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