Transcriptome Profiling of Petal Abscission Zone and Functional Analysis of an Aux/IAA Family Gene RhIAA16 Involved in Petal Shedding in Rose

Abstract

Roses are one of the most important cut flowers among ornamental plants. Rose flower longevity is largely dependent on the timing of petal shedding occurrence. To understand the molecular mechanism underlying petal abscission in rose, we performed transcriptome profiling of the petal abscission zone during petal shedding using Illumina technology. We identified a total of 2592 differentially transcribed genes (DTGs) during rose petal shedding. Gene ontology term enrichment and pathway analysis revealed that major biochemical pathways the DTGs were involved in included ethylene biosynthesis, starch degradation, superpathway of cytosolic glycolysis, pyruvate dehydrogenase and TCA cycle, photorespiration and the lactose degradation III pathway. This suggests that alterations in carbon metabolism are an important part of rose petal abscission. Among these DTGs, approximately 150 genes putatively encoding transcription factors were identified in rose abscission zone. These included zinc finger, WRKY, ERF, and Aux/IAA gene families, suggesting that petal abscission involves complex transcriptional reprogramming. Approximately 108 DTGs were related to hormone pathways, of which auxin and ethylene related DTGs were the largest groups including 52 and 41 genes, respectively. These also included 12 DTGs related to gibberellin and 6 DTGs in jasmonic acid pathway. Surprisingly, no DTGs involved in the biosynthesis/signaling of abscisic acid, cytokinin, brassinosteroid, and salicylic acid pathways were detected. Moreover, among DTGs related to auxin, we identified an Aux/IAA gene RhIAA16 that was up-regulated in response to petal shedding. Down-regulation of RhIAA16 by virus-induced gene silencing in rose promoted petal abscission, suggesting that RhIAA16 plays an important role in rose petal abscission.

Rosa hybrida RhERF1 and RhERF4 mediate ethylene‐ and auxin‐regulated petal abscission by influencing pectin degradation

“…The expression of RhERF1 was significantly reduced by ethylene treatment, while the expression of RhERF4 was significantly induced by auxin (Figure a,b). We then examined the expression of RhERF1 and RhERF4 in the petal AZ during six sequential stages of flower opening as described previously (Gao et al ., ). Quantitative real‐time (qRT)‐PCR analysis showed that RhERF1 transcript levels decreased (Figure c), while RhERF4 expression was the highest in stage 2 and then decreased (Figure d).…”

“…For expression pattern analysis, flower opening stages were defined as previously described (Gao et al ., ). Briefly these are: stage 1, bud with completely opened sepal; stage 2, bud with outermost petal layer loosened; stage 3, flower with outermost petal layer opened; stage 4, flower with inner petal layer loosened; stage 5, fully opened flower with visible anthers; stage 6, fully opened flower with abscised petals.…”

“…The distal side of the separation layer is connected to the petal and the proximal side of the separation layer is adjacent to the receptacle. Petal AZ samples were collected by excising the base of the petals (<2 mm in length) and the area of the receptacles connected to the petals (<2 mm in length) (Gao et al ., ). The petal samples were collected from the middle whorl of the flowers (Wu et al ., ).…”

“…The raw reads have been deposited into the NCBI SRA database (PRJNA523893). The RNA‐seq data were processed, assembled and annotated as previously described (Gao et al ., ). The RNA‐seq reads were examined to remove low‐quality ( Q ‐value < 20) reads and adapters using Trimmomatic (Bolger et al ., ).…”

Graft-accelerated virus-induced gene silencing facilitates functional genomics in rose flowers

“…After vacuum agroinoculation, the plantlets are transferred to soil. TRV‐infected plantlets flower about 2 months post‐inoculation, upon which time the efficiency can be evaluated by observing flower characteristics, such as flower development (Chen et al ), abscission (Gao et al ), and petal expansion (Ma et al ; Luo et al ).…”