Proteome Analysis of the Gametophytes of a Western Himalayan Fern Diplazium maximum Reveals Their Adaptive Responses to Changes in Their Micro-Environment.

Bhuvnesh Sareen,Robin Joshi,Amita Bhattacharya,Pooja Thapa

doi:10.3389/fpls.2019.01623

Abstract

Ferns have survived changing habitats and environmental extremes of different eras, wherein, the exploratory haploid gametophytes are believed to have played a major role. Therefore, the proteome of in vitro grown gametophytes of a temperate Himalayan fern, Diplazium maximum in response to 0 (G0), 1 (G1), and 3% (G3) sucrose was studied. A total of 110 differentially abundant protein spots (DAPs) were obtained. Among these, only 67 could be functionally categorized as unique proteins involved in various metabolic processes. Calcium dependent proteins, receptor like kinases, G proteins, proteins related to hormonal signaling and their interaction with other pathways, and regulatory proteins were recorded indicating the involvement of five different signaling pathways. DAPs involved in the activation of genes and transcription factors of signaling and transduction pathways, transport and ion channels, cell-wall and structural proteins, defense, chaperons, energy metabolism, protein synthesis, modification, and turnover were identified. The gametophytes responded to changes in their micro-environment. There was also significant increase in prothallus biomass and conversion of two-dimensional prothalli into three-dimensional prothallus clumps at 3% sucrose. The three-D clumps had higher photosynthetic surface area and also closer proximity for sexual reproduction and sporophyte formation. Highest accumulation of proline, enhanced scavenging of reactive oxygen species (ROS) and DAPs of mostly, abiotic stress tolerance, secondary metabolite synthesis, and detoxification at 3% sucrose indicated an adaptive response of gametophytes. Protein Protein Interaction network and Principal Component analyses, and qRT-PCR validation of genes encoding 12 proteins of various metabolic processes indicated differential adjustment of gametophytes to different levels of sucrose in the culture medium. Therefore, a hypothetical mechanism was proposed to show that even slight changes in the micro-environment of D. maximum gametophytes triggered multiple mechanisms of adaptation. Many DAPs identified in the study have potential use in crop improvement and metabolic engineering programs, phytoremediation and environmental protection.

Highlights

The huge diversity of extant ferns that we see today is part of a lineage that diverged from other vascular plants in the Paleozoic era itself
Surface sterilized spores suspended in 1.0 ml of sterile de-ionized water were inoculated on 0.8% agar (w/v) gelled, full strength Knop's (1865) medium (KM) at pH, 5.75 in 90 mm Petri plates
While rhizoidsbearing protonema developed after 30–32 days, formation of spatulate stage was recorded after 37–40 days

Summary

Introduction

The huge diversity of extant ferns that we see today is part of a lineage that diverged from other vascular plants in the Paleozoic era itself. Innate abilities like functional and physiological shifts, phytochromes for reception of low light, desiccation tolerance, and flexible reproductive strategies have empowered ferns to adapt and persist under extreme selection pressures (Page, 2002; Suetsugu et al, 2005; Watkins et al, 2007). As a result, this group of plants has evolved into a unique flora with ability to adapt in novel niches (Suetsugu et al, 2005; Watkins et al, 2007; Watkins and Cardelús, 2012; Pittermann et al, 2013). Gametophytes are believed to have evolved specific traits for more efficient adaptation to stressful environments than sporophytes (Watkins et al, 2007; Pittermann et al, 2013)

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Results

Conclusion