Global Transcriptomic Analysis Reveals the Mechanism of Phelipanche aegyptiaca Seed Germination

Abstract

Phelipanche aegyptiaca is one of the most destructive root parasitic plants of Orobanchaceae. This plant has significant impacts on crop yields worldwide. Conditioned and host root stimulants, in particular, strigolactones, are needed for unique seed germination. However, no extensive study on this phenomenon has been conducted because of insufficient genomic information. Deep RNA sequencing, including de novo assembly and functional annotation was performed on P. aegyptiaca germinating seeds. The assembled transcriptome was used to analyze transcriptional dynamics during seed germination. Key gene categories involved were identified. A total of 274,964 transcripts were determined, and 53,921 unigenes were annotated according to the NR, GO, COG, KOG, and KEGG databases. Overall, 5324 differentially expressed genes among dormant, conditioned, and GR24-treated seeds were identified. GO and KEGG enrichment analyses demonstrated numerous DEGs related to DNA, RNA, and protein repair and biosynthesis, as well as carbohydrate and energy metabolism. Moreover, ABA and ethylene were found to play important roles in this process. GR24 application resulted in dramatic changes in ABA and ethylene-associated genes. Fluridone, a carotenoid biosynthesis inhibitor, alone could induce P. aegyptiaca seed germination. In addition, conditioning was probably not the indispensable stage for P. aegyptiaca, because the transcript level variation of MAX2 and KAI2 genes (relate to strigolactone signaling) was not up-regulated by conditioning treatment.

Transcriptome analysis of Phelipanche aegyptiaca seed germination mechanisms stimulated by fluridone, TIS108, and GR24

“…The seed samples (1 g) were separately ground in liquid N using a mortar and pestle. The concentrations of ABA and GA were quantified using appropriate enzyme-linked immunosorbent assay kits (Chengling, Beijing, China) according to manufacturer’s instructions [ 11 ]. The ABA and GA concentrations are reported as the mean of three biological replicates.…”

“…Six plant-hormone-related genes, two SL perception-related genes, and two genes related to P450s were selected for validation of RNA-seq by qRT-PCR. PaTubulin1 was used as an internal control [ 11 , 22 ]. The qRT-PCR was conducted using SYBR GreenER™ qPCR SuperMix Universal (Invitrogen, Gaithersburg, MD, USA).…”

“…The seeds remain viable for up to 20 years in soil in the absence of a suitable host[ 4 ]. Broomrape seeds require chemical stimulants secreted by host roots to germinate, and the seedlings must contact the host root within a few days to survive [ 11 ]. It has been suggested that synthetic or natural chemicals could be used to reduce seedbanks by stimulating seed germination in the absence of suitable hosts.…”

“…aegyptiaca seeds must be conditioned for 4 to 7 d in a humid environment before GR24 can stimulate high germination rates. During conditioning, gibberellin (GA) is synthesized and plays an important role in subsequent germination[ 11 ]. Fluridone (FL), a carotenoid biosynthesis inhibitor, shortens the conditioning period required for O .…”

Recent research progress in combatting root parasitic weeds

“…Structure modification of artificial germination stimulants resulted in an improvement in the germination-inducing activity [173][174][175][176]. Although conditioning prior to applying artificial germination stimulants was a prerequisite for the success of a suicidal germination approach [169,171], Yao et al [177] reported that conditioning was probably not the indispensable stage of P. aegyptiaca based on the finding that the transcript level of genes relating to SL signalling was not up-regulated by the conditioning treatment.…”