Recombinant artificial forisomes provide ample quantities of smart biomaterials for use in technical devices

Abstract

Forisomes are mechanoproteins that undergo ATP-independent contraction-expansion cycles triggered by divalent cations, pH changes, and electrical stimuli. Although native forisomes from Medicago truncatula comprise a number of subunits encoded by separate genes, here we show that at least two of those subunits (MtSEO1 and MtSEO4) can assemble into homomeric forisome bodies that are functionally similar to their native, multimeric counterparts. We expressed these subunits in plants and yeast, resulting in the purification of large quantities of artificial forisomes with unique characteristics depending on the expression platform. These artificial forisomes were able to contract and expand in vitro like native forisomes and could respond to electrical stimulation when immobilized between interdigital transducer electrodes. These results indicate that recombinant artificial forisomes with specific characteristics can be prepared in large amounts and used as components of microscale and nanoscale devices.

Sieve element occlusion(SEO) genes encode structural phloem proteins involved in wound sealing of the phloem

“…We recently reported that two M. truncatula SEO proteins (MtSEO-F1 and MtSEO-F4) assemble into spindle-like structures similar to native forisomes (Fig. 3A) when coexpressed as tagged and untagged versions in N. benthamiana (25,27), demonstrating the validity of this approach for the analysis of NtSEO assembly.…”

“…All fusion constructs were assembled in the pBShrGFP vector series containing the hrGFP (65) coding sequence fused to the CaMV 35S terminator. Fusions were obtained for NtSEO1, NtSEO2, and, as a control, forisome subunitencoding MtSEO-F1 (24,27). The detailed cloning procedure is given in SI Materials and Methods.…”

“…Thus far, four sieve element occlusion (SEO) gene family members have been identified in Medicago truncatula (MtSEO-F1-F4) and Glycine max (GmSEO-F1-F4) and characterized as encoding forisome subunits, which assemble into a special type of crystalloid P-protein found uniquely in Fabaceae (23)(24)(25)(26)(27)(28). Forisomes differ from conventional P-proteins because they can undergo a reversible switch between condensed spindle-shaped and dispersed plug-forming states, triggered by a calcium influx (29,30).…”

Calcium powered phloem protein ofSEOgene family “Forisome” functions in wound sealing and act as biomimetic smart materials

“…Forisome smart materials are known to be capable of self assembly consisting of fibers of nanometer range. 46 Self assembly of forisome smart materials in heterologous background of N. benthamiana results in transient expression in epidermal cells. 35 It is therefore remarkable that forisomes can assemble in heterologous background.…”

“…36.,37 Through the studies of Knoblauch it became evident that occlusion of sieve tube pores by crystalloid P-proteins is rapidly reversible and controlled by the Ca 2+ ñux. 46,47 On the basis of dynamic structural changes which are unique to the crystalline P-proteins of legumes distinguishes them from the non-dispersive phloem-specific protein bodies of other families (such as Urticaceae and Rosaceae). 48 Classically the phloem protein bodies have been classified namely into 2 broad categories.…”