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

Abstract

P. aegyptiaca is one of the most destructive root parasitic plants worldwide, causing serious damage to many crop species. Under natural conditions P. aegyptiaca seeds must be conditioned and then stimulated by host root exudates before germinating. However, preliminary experiments indicated that TIS108 (a triazole-type inhibitor of strigolactone) and fluridone (FL, an inhibitor of carotenoid-biosynthesis) both stimulated the germination of P. aegyptiaca seeds without a water preconditioning step (i.e. unconditioned seeds). The objective of this study was to use deep RNA sequencing to learn more about the mechanisms by which TIS108 and FL stimulate the germination of unconditioned P. aegyptiaca seeds. Deep RNA sequencing was performed to compare the mechanisms of germination in the following treatments: (i) unconditioned P. aegyptiaca seeds with no other treatment, (ii) unconditioned seeds treated with 100 mg/L TIS108, (iii) unconditioned seeds treated with 100 mg/L FL + 100 mg/L GA3, (iv) conditioned seeds treated with sterile water, and (v) conditioned seeds treated with 0.03 mg/L GR24. The de novo assembled transcriptome was used to analyze transcriptional dynamics during seed germination. The key gene categories involved in germination were also identified. The results showed that only 119 differentially expressed genes were identified in the conditioned treatment vs TIS108 treatment. This indicated that the vast majority of conditions for germination were met during the conditioning stage. Abscisic acid (ABA) and gibberellic acid (GA) played important roles during P. aegyptiaca germination. The common pathway of TIS108, FL+GA3, and GR24 in stimulating P. aegyptiaca germination was the simultaneous reduction in ABA concentrations and increase GA concentrations. These results could potentially aid the identification of more compounds that are capable of stimulating P. aegyptiaca germination. Some potential target sites of TIS108 were also identified in our transcriptome data. The results of this experiment suggest that TIS108 and FL+GA3 could be used to control P. aegyptiaca through suicidal germination.

Comparative transcriptome analysis revealing the potential mechanism of seed germination stimulated by exogenous gibberellin in Fraxinus hupehensis

“…Thus, although both water and GA 3 treatments promoted seed germination and required more energy for seed germination, exogenous GA 3 accelerated the TCA cycle to release more energy for seed germination by up-regulating PDHB . These respiratory pathways are critical for providing energy for various cellular functions during seed germination, as described in our study [32, 36]. Most of this energy was produced during germination, especially after GA 3 treatment.…”

“…A considerable amount of energy is required during seed germination, and all biochemical reactions in plants enter the TCA cycle, providing power for the mitochondrial electron transport chain to generate ATP [31]. The energy required during seed germination mainly comes from glycolysis, pentose phosphate pathway, and the TCA cycle of cellular respiration [32]. The ATP content in dry seeds is low but gradually increases after seed germination, which proves that the respiratory pathway plays an important role in seed germination [33, 34].…”

“…NCED rapidly catalyzes the synthesis of ABA when seeds absorber water and is a key enzyme for ABA synthesis [55], whereas CYP707A is the core enzyme of ABA degradation [56]. The expression levels of ABA metabolic genes are associated with inhibition of seed germination [20, 32]. In the current study, the expression level of NCED in the dormant seeds of F. hupehensis was significantly higher than that in germinated seeds, but no significant difference was observed in the seeds after germination.…”

Transcriptome Analysis of Jojoba (Simmondsia chinensis) during Seed Development and Liquid Wax Ester Biosynthesis

“…Transcriptome sequencing (de novo or resequencing) is a powerful approach to investigate changes in global gene expression during plant growth and development. It has been employed to study gene expression during seed germination in Phelipanche aegyptiaca [19], floral initiation in Pongamia pinnata [20], seed development in pecan trees (Carya illinoinensis) [21], seed development in Camelina sativa [22], seed development in Euryale ferox [23], and seed development in Millettia pinnata [24]. Transcriptome analysis has also been employed to study oil biosynthesis in Pongamia pinnata [20], oil content and fatty acid composition in Camellia oleifera [25], lipid metabolism in pecan trees seeds (Carya illinoinensis) seeds (21), alpha-linolenic acid synthesis in tree peony seeds [26], triacylglycerol biosynthesis in Camelina sativa [22], oil accumulation in Millettia pinnata [24], and the biosynthesis of unsaturated fatty acids in Perilla frutescens [27].…”

Triazolide strigolactone mimics as potent selective germinators of parasitic plant Phelipanche ramosa

“…Unlike Striga seeds, which require high preconditioning temperatures and thus they are active especially in Sub‐Saharan regions of Africa, broomrapes germinate at lower temperatures thus affecting vast areas in Asia, Australia, Central America, Northern Africa and Mediterranean regions in Europe, also spreading to Central and Eastern Europe . Several types of rhizosphere signals triggering seed germination of parasitic plants and belonging to plant secondary metabolites or fungal metabolites, such as strigolactones, isothiocyanates, sesquiterpene lactones, dehydrocostus lactone, fusicoccins and ophiobolin A, have been recognized, with natural strigolactones being the most potent . Very recently, a strigolactone mimic called sphynolactone‐7 was found to induce Striga hermonthica seed germination at femtomolar level, thus resembling the potency of natural strigolactones, namely of 5‐deoxystrigol .…”