Comprehensive Biochemical, Physiological, and Transcriptomic Analyses Provide Insights Into Floral Bud Dormancy in Rhododendron delavayi Franch

Abstract

Due to a scarcity of relevant data, the ornamental woody flowerRhododendron delavayiFranch. is examined in the current study for its low temperature-induced floral bud dormancy (late October–end December) aspect. This study used transcriptome data profiling and co-expression network analyses to identify the interplay between endogenous hormones and bud dormancy phases such as pre-dormancy, para-dormancy, endo-dormancy, eco-dormancy, and dormancy release. The biochemical and physiological assays revealed the significance of the abundance of phytohormones (abscisic acid, auxin, zeatin, and gibberellins), carbohydrate metabolism, oxidative species, and proteins (soluble proteins, proline, and malondialdehyde) in the regulatory mechanism of floral bud dormancy. The transcriptome sequencing generated 65,531 transcripts, out of which 504, 514, 307, and 240 expressed transcripts were mapped uniquely to pre-, para-, endo-, and eco-phases of dormancy, showing their roles in the stimulation of dormancy. The transcripts related toLEA29,PGM,SAURfamily,RPL9e,ATRX,FLOWERING LOCUS T,SERK1,ABFs,ASR2, andGID1were identified as potential structural genes involved in floral bud dormancy. The transcription factors, includingZinc fingers,CAD,MADS-boxfamily,MYB, andMYC2,revealed their potential regulatory roles concerning floral bud dormancy.The gene co-expression analysis highlighted essential hub genes involved in cold stress adaptations encoding proteins,viz,SERPIN,HMA,PMEI,LEA_2,TRX,PSBT, andAMAT. We exposed the connection among low temperature-induced dormancy in floral buds, differentially expressed genes, and hub genesviastrict screening steps to escalate the confidence in selected genes as being truly putative in the pathways regulating bud dormancy mechanism. The identified candidate genes may prove worthy of further in-depth studies on molecular mechanisms involved in floral bud dormancy ofRhododendronspecies.