AUTHOR=Fan Songle , Jia Yongxia , Wang Rong , Chen Xiaoyong , Liu Wanzhen , Yu Hui 

TITLE=Multi-omics analysis the differences of VOCs terpenoid synthesis pathway in maintaining obligate mutualism between Ficus hirta Vahl and its pollinators

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1006291

DOI=10.3389/fpls.2022.1006291

ISSN=1664-462X

ABSTRACT=<sec><title>Inroduction</title><p>Volatile organic compounds (VOCs) emitted by the receptive syconia of <italic>Ficus</italic> species is a key trait to attract their obligate pollinating fig wasps. <italic>Ficus hirta</italic> Vahl is a dioecious shrub, which is pollinated by a highly specialized symbiotic pollinator in southern China. Terpenoids are the main components of VOCs in <italic>F. hirta</italic> and play ecological roles in pollinator attraction, allelopathy, and plant defense. However, it remains unclear that what molecular mechanism difference in terpenoid synthesis pathways between pre-receptive stage (A-phase) and receptive stage (B-phase) of <italic>F. hirta</italic> syconia.</p></sec><sec><title>Methods</title><p>Transcriptome, proteome and Gas Chromatography-Mass Spectrometer (GC-MS) were applied here to analyze these difference.</p></sec><sec><title>Results and discussion:</title><p>Compared to A-phase syconia, the genes (<italic>ACAT2</italic>, <italic>HMGR3</italic>, <italic>GGPS2</italic>, <italic>HDR</italic>, <italic>GPS2</italic>, <italic>TPS2</italic>, <italic>TPS4</italic>, <italic>TPS10-4</italic>, <italic>TPS14</italic>) related to the terpenoid synthesis pathway had higher expression level in receptive syconia (B-phase) according to transcriptome sequencing. Seven differentially expressed transcription factors were screened, namely <italic>bHLH7</italic>, <italic>MYB1R1</italic>, <italic>PRE6</italic>, <italic>AIL1</italic>, <italic>RF2b</italic>, <italic>ANT</italic>, <italic>VRN1</italic>. Specifically, <italic>bHLH7</italic> was only specifically expressed in B-phase. 235 differentially expressed proteins (DEPs) were mainly located in the cytoplasm and chloroplasts. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEPs were mainly enriched in the metabolic process. A total of 9 terpenoid synthesis proteins were identified in the proteome. Among them, 4 proteins in methylerythritol phosphate (MEP) pathway were all down-regulated. Results suggested the synthesis of terpenoids precursors in B-phase bracts were mainly accomplished through the mevalonic acid (MVA) pathway in cytoplasm. Correlation analysis between the transcriptome and proteome, we detected a total of 1082 transcripts/proteins, three of which are related to stress. From the VOCs analysis, the average percent of monoterpenoids emitted by A-phase and B-phase syconia were 8.29% and 37.08%, while those of sesquiterpenes were 88.43% and 55.02% respectively. Monoterpenes (camphene, myrcene, camphor, menthol) were only detected in VOCs of B-phase syconia. To attract pollinators, B-phase syconia of <italic>F. hirta</italic> need more monoterpenoids and less sesquiterpenes. We speculate that transcription factor <italic>bHLH7</italic> may regulate the terpenoid synthesis pathway between A- and B-phase syconia. Our research provided the first global analysis of mechanism differences of terpenoid synthesis pathways between A and B phases in <italic>F. hirta</italic> syconia.</p></sec>