Physiological response of sunflowers to broomrape parasitism and analysis of the key metabolic pathways

Abstract

[Objective] To study the physiological response of sunflowers to broomrape parasitism and the related metabolic pathways, as well as understanding the molecular mechanism of sunflower resistance to broomrape parasitism. [Methods] The broomrape-resisant (s41) and -sensitive (s26) sunflowers were used as the testing materials. Transcriptome analysis of 4 samples under the condition of parasitic stress was carried out, and physiological verification analysis of key metabolites was carried out. [Results] (1) Under inoculation, the plant height and root number of susceptible materials were affected significantly, and some of them were even unearthed, while the resistant materials had no obvious changes, and only a few were parasitized. (2) The number of DEGs was 6 362, 6 609, 5 490 and 5 469 by screening the differential genes among the samples. GO analysis showed that the four comparison groups, namely s26-s41, s26CK-s41CK, s26-s26CK, and s41-s41CK, had the most differential genes in biological processes, followed by cellular components, and less in molecular functions. KEGG analysis showed that infection had a great influence on plant signal transduction, biosynthesis of secondary metabolites, lipid metabolism, amino acid metabolism, and sugar metabolism in sunflowers. (3) Physiological analyses found that the phenylalanine deaminase, cinnamyl alcohol dehydrogenase, glutathione, total phenols, and salicylic acid showed an upward trend, indicating that the stress tolerant system was activated under parasitism. However, the trend of the physiological indicators of the sensitive and tolerant materials were different. Also, the genes controlling the physiological responses were differentially expressed. [Conclusion] It was found that inoculation with broomrape significantly affected the plant height and root volume of the susceptible materials, while the resistant materials were not affected. The resistant materials were enhanced in root lignin synthesis, antioxidant enzyme activity, and the expression of key genes of phenylpropanoid metabolism, salicylic acid and signaling pathway, and hence increased the resistance to broomrape.

Keywords

• orobanche cumana
• helianthus annuus
• transcriptome
• physiological response
• metabolic pathway