The Occurrence of Calcium Oxalate Crystals and Distribution of Arabinogalactan Proteins (AGPs) in Ovary Cells During Fragaria x ananassa (Duch.) Development

Abstract

In this study, the presence of calcium oxalate crystals and distribution of arabinogalactan proteins (AGPs) in the ovary of Fragaria x ananassa (Duchesne) were investigated. The arrangement of the AGP epitopes was analyzed using immunohistochemistry techniques with JIM13, JIM15, and MAC207 monoclonal antibodies. To confirm the immunofluorescence studies, experiments at the subcellular level were performed with the immunogold method using transmission electron microscopy. We observed calcium oxalate crystals as druses in the middle layer of the ovary, which created a distinct ring-like immunofluorescence pattern around the ovule, indicating the presence of AGP epitopes. We propose hypotheses concerning the roles of calcium oxalate crystals in ovaries: the occurrence of crystals in the external part of the ovary may constitute a mechanical barrier against herbivores (1) the presence of AGPs in close proximity to calcium oxalate crystals may support their role as a calcium depository, which is important for the developing embryo and seed coat formation as well as in the interaction between pollen tubes and female gametophyte during sexual plant reproduction (2).

Immunodetection of Pectic Epitopes, Arabinogalactan Proteins, and Extensins in Mucilage Cells from the Ovules of Pilosella officinarum Vaill. and Taraxacum officinale Agg. (Asteraceae)

“…According to Leszczuk et al [ 42 ], AGPs are involved in establishment of the cell wall, namely the plasma membrane continuum. During maturation in Pilosella and Taraxacum , mucilage cells undergo an intense period of secretory activity, which leads to dramatic cytological changes in the relationship between the cell wall and the plasma membrane [ 31 , 35 ].…”

“…Leszczuk et al [ 42 ] showed the presence of AGPs labeled with JIM13 and JIM15 in close proximity to calcium oxalate (CaOx) crystals in the ovary wall of Fragaria × ananassa (Rosaceae). These authors were successful in performing an immunogold reaction, which confirmed the presence of AGPs at the edge of the CaOx crystals.…”

“…Leszczuk et al [ 42 ] proposed an attractive hypothesis: “Crystals associated with AGPs may serve dual functions: deposition of calcium ions important for the developing embryo and seed coat formation as well as involvement in the earliest events during sexual plant reproduction—the interaction between pollen tubes and female gametophyte getting ready for fertilization”. Our results are in agreement with the results of Leszczuk et al [ 42 ]. However, we also observed an association between AGPs and CaOx in the ovules of apomicts, which do not require fertilization ( Taraxacum officinale ).…”

“…Recently, Leszczuk et al [ 42 ] showed an association between arabinogalactan proteins and calcium oxalate crystals in the ovaries of Fragaria × ananassa . Calcium oxalate crystals are a common characteristic of ovular cells of Asteraceae [ 43 , 44 , 45 ].…”

New insights into the functions of carbon–calcium inclusions in plants

“…Calreticulin affects intracellular Ca 2+ homoeostasis by modulation of endoplasmic reticulum Ca 2+ storage and transport (Michalak et al ., 1999; Nakata et al ., 2003). Recently it was found that CaOx crystals in ovary cells are associated with arabinogalactan proteins that could act as calcium binding and storage molecules (Leszczuk et al ., 2019). Moreover several substances accumulate within the vacuoles of crystal cells, some of them with strong Ca‐binding capacity.…”