Maternal environment alters dead pericarp biochemical properties of the desert annual plant Anastatica hierochuntica L.

Abstract

The dead organs enclosing embryos (DOEEs) emerge as central components of the dispersal unit (DU) capable for long-term storage of active proteins and other substances that affect seed performance and fate. We studied the effect of maternal environment (salt and salt+heat) on progeny DU (dry indehiscent fruit) focusing on pericarp properties of Anastatica hierochuntica. Stressed plants displayed increased seed abortion and low level and rate of germination. Hydrated pericarps released antimicrobial factors and allelopathic substances that inhibit germination of heterologous species. Proteome analysis of dead pericarps revealed hundreds of proteins, among them nucleases, chitinases and proteins involved in reactive oxygen species detoxification and cell wall modification. Salt treatment altered the composition and level of proteins stored in the pericarp. We observed changes in protein profile released from seeds of salt-treated plants with a notable increase in a small anti-fungal protein, defensin. The levels of phytohormones including IAA, ABA and salicylic acid were reduced in dead pericarps of stressed plants. The data presented here highlighted the predominant effects of maternal environment on progeny DUs of the desert plant A. hierochuntica, particularly on pericarp properties, which in turn might affect seed performance and fate, soil fertility and consequently plant biodiversity.

Dead but Not Dead End: Multifunctional Role of Dead Organs Enclosing Embryos in Seed Biology

“…The proteomic data also listed S1 type endonucleases in seed coats and pericarps of A. hierochuntica [1,19,30] whose activity was reduced following exposure to salt or to a combination of salt and heat [30]. On the other hand, proteases commonly accumulated in DOEEs showed a significant increase in activity in pericarps derived from Anastatica plants treated with salt and heat [30]. Endonuclease as well as protease activities were enhanced in husks derived from A. sterilis plants experiencing drought [19].…”

“…Other proteins implicated in conferring resistance to pathogenic fungi include chitinases and gluconases [33][34][35]. The proteomic data also listed S1 type endonucleases in seed coats and pericarps of A. hierochuntica [1,19,30] whose activity was reduced following exposure to salt or to a combination of salt and heat [30]. On the other hand, proteases commonly accumulated in DOEEs showed a significant increase in activity in pericarps derived from Anastatica plants treated with salt and heat [30].…”

“…PCD involves the degradation of almost all macromolecules such as DNA, RNA, and proteins whose constituents are remobilized into other plant parts [27][28][29]. Recent reports, however, have demonstrated a type of PCD occurring in seed coverings where hundreds of proteins remain intact and can persist in active form for decades, and are released to the immediate surrounding of the dispersal unit upon hydration [16,19,30,31].…”

“…Proteome analysis performed on proteins extracted from DOEEs of various plant species revealed hundreds of proteins, which were categorized into multiple molecular function groups including catalytic activity, binding activity, hydrolase, pectinesterase, and oxireductase activities. Classification for biological processes showed that many of the released proteins are involved in metabolic processes and oxidation-reduction processes as well as in response to stimulus [1,19,30]. Within the group of proteins responsive to biotic and abiotic stimulus are several defensin-like (DEFL) proteins involved in response to pathogenic fungi [32].…”

“…Within the group of proteins responsive to biotic and abiotic stimulus are several defensin-like (DEFL) proteins involved in response to pathogenic fungi [32]. Indeed, a higher level (24-fold) of defensin was released from Anastatica hierochuntica seeds derived from plants subjected to salt stress compared to seeds from non-stressed plants [30]. Other proteins implicated in conferring resistance to pathogenic fungi include chitinases and gluconases [33][34][35].…”