Flower bud proteome reveals modulation of sex-biased proteins potentially associated with sex expression and modification in dioecious Coccinia grandis

Abstract

Background Dioecy is an important sexual system wherein, male and female flowers are borne on separate unisexual plants. Knowledge of sex-related differences can enhance our understanding in molecular and developmental processes leading to unisexual flower development. Coccinia grandis is a dioecious species belonging to Cucurbitaceae, a family well-known for diverse sexual forms. Male and female plants have 22A + XY and 22A + XX chromosomes, respectively. Previously, we have reported a gynomonoecious form (22A + XX) of C. grandis bearing morphologically hermaphrodite flowers (GyM-H) and female flowers (GyM-F). Also, we have showed that foliar spray of AgNO 3 on female plant induces morphologically hermaphrodite bud development (Ag-H) despite the absence of Y-chromosome. Results To identify sex-related differences, total proteomes from male, female, GyM-H and Ag-H flower buds at early and middle stages of development were analysed by label-free proteomics. Protein search against the cucumber protein sequences (Phytozome) as well as in silico translated C. grandis flower bud transcriptome database, resulted in the identification of 2426 and 3385 proteins (FDR ≤ 1%), respectively. The latter database was chosen for further analysis as it led to the detection of higher number of proteins. Identified proteins were annotated using BLAST2GO pipeline. SWATH-MS-based comparative abundance analysis between Female_Early_vs_Male_Early, Ag_Early_vs_Female_Early, GyM-H_Middle_vs_Male_Middle and Ag_Middle_vs_ Male_Middle led to the identification of 650, 1108, 905 and 805 differentially expressed proteins, respectively, at fold change ≥1.5 and P ≤ 0.05. Ethylene biosynthesis-related candidates as highlighted in protein interaction network were upregulated in female buds compared to male buds. AgNO 3 treatment on female plant induced proteins related to pollen development in Ag-H buds. Additionally, a few proteins governing pollen germination and tube growth were highly enriched in male buds compared to Ag-H and GyM-H buds. Conclusion Overall, current proteomic analysis provides insights in the identification of key proteins governing dioecy and unisexual flower development in cucurbitaceae, the second largest horticultural family in terms of economic importance. Also, our results suggest that the ethylene-mediated stamen inhibition might be conserved in dioecious C. grandis similar to its monoecious cucurbit relatives. Further, male-biased proteins associated with pollen germination and tube growth identified here can help in understanding pollen fertility. Electronic supplementary material The online version of this article (10.1186/s12870-019-1937-1) contains supplementary material, which is available to authorized users.

Comparative RNA-Seq analysis reveals genes associated with masculinization in female Cannabis sativa

“…However, epigenetic elements (e.g., DNA methylation and small regulatory RNA molecules), environmental cues (e.g., light and nutrients), plant hormones (e.g., auxin, gibberellins and abscisic acid), and chemical agents (e.g., silver thiosulfate and silver nitrate) can influence plant sex via as of yet unknown mechanisms (Ram and Jaiswal 1972; Galoch 1978;Ram and Sett 1982;Truta et al 2007;Borthwick and Scully 1954). Foliar application of chemicals, such as silver thiosulfate or silver nitrate, can induce male organ development in genetically female background of several dioecious plant species, including Asparagus officinalis, Ricinus communis, Coccinia grandis and C. Sativa (Mohan Ram and Sett 1980;Ram and Sett 1982;Devani et al 2017;Li et al 2017). Although genomic and proteomic approaches have been used to examine chemical-based sexual expression in dioecious A. officinalis and C. grandis (Devani et al 2017(Devani et al , 2019Li et al 2017), the molecular mechanism of this phenomenon remains unknown.…”

“…Foliar application of chemicals, such as silver thiosulfate or silver nitrate, can induce male organ development in genetically female background of several dioecious plant species, including Asparagus officinalis, Ricinus communis, Coccinia grandis and C. Sativa (Mohan Ram and Sett 1980;Ram and Sett 1982;Devani et al 2017;Li et al 2017). Although genomic and proteomic approaches have been used to examine chemical-based sexual expression in dioecious A. officinalis and C. grandis (Devani et al 2017(Devani et al , 2019Li et al 2017), the molecular mechanism of this phenomenon remains unknown. In this study, we generated chemically induced male flower buds in genetically female C. sativa plants, and employed comparative RNA-Seq analyses among induced-male flowers, normal female flowers and normal male flowers to identify genes that mediate the expression of the opposite sex in predisposed female plants.…”

“…Comparative transcriptomic analysis has been widely used between male and female flowers in a few dioecious plants, for example in C. grandis and A. officinalis, to explore sex-linked genes, or silver nitrate (AgNO 3 )-induced sex-biased genes that could play roles in flower sex determination (Devani et al 2017;Li et al 2017). A proteomic approach was also employed to identify proteins associated with AgNO 3 -induced sexual expression in C. grandis (Devani et al 2019). These studies identified several transcripts linked to flower sex expression and floral development, including those in controlling aspects of plant hormone signaling.…”

“…There is, therefore, an interest in understanding the molecular basis of male flower development in cannabis. In this context, the application of silver thiosulfate or silver nitrate has a masculinizing effect, and can induce the development of male flowers in female plants ( Mohan Ram and Sett 1980;Ram and Sett 1982;Devani et al 2017;Li et al 2017). In this study, we treated genetically female plants with silver thiosulfate (Ag 2 S 2 O 3 ) complex to induce male floral organs, and employed a comparative RNA-Seq study to identify genes involved in Ag 2 S 2 O 3 -mediated sex modification and flower development.…”

The genetic basis of sex determination in grapevines (Vitis spp.)

“…Likewise, SKU5 is up-regulated in mature cucumber pollen grains; it was proposed that SKU5 may function during cucumber floral development and pollen formation (Pawełkowicz et al, 2019) and is generally associated with two-directional growth and the regulation of cell wall expansion (Sedbrook et al, 2002). M-linked polymorphisms were found within an aldolase-coding gene; a proteomic study of pumpkin nectar found an aldolase uniquely in male nectar (Chatt et al, 2018), and a putative aldolase- (Devani et al, 2019). Based on these functions, the genes in this region appear to enhance maleness, and existing literature has not associated these genes explicitly with pistil fertility to the authors knowledge.…”