PA1b, a plant peptide, induces intracellular [Ca^(2+)] in- crease via Ca^(2+) influx through the L-type Ca^(2+) channel and triggers secretion in pancreatic β cells

Using alginic acid to adsorb polypeptides at pH 2.7, we isolated a peptide pea albumin 1b (PA1b) from pea seeds. The PA1b is a single chain peptide consisting of 37 amino acid residues with 6 cysteines which constitutes the cystine-knot structure. Using microfluorometry and patch clamp techniques, we found that PA1b significantly elevated the intracellular calcium level ([Ca2+ ]i) and elicited membrane capacitance increase in the primary rat pancreatic β cells. The PA1b effect on [Ca2+]i elevation was abolished in the absence of extracellular Ca2+ or in the presence of L-type Ca2+ channel blocker, ni- modipine. Interestingly, we found that PA1b significantly depolarized membrane potential, which could lead to the opening of voltage-dependent L-type Ca2+ channels and influx of extracellular Ca2+, and then evoke robust secretion. In this study we identified the plant peptide PA1b which is capable of affecting the excitability and function of mammalian pancreatic β cell.

Research progress of plant antimicrobial peptides

Plant antimicrobial peptides are a very large family of antimicrobial peptides,which have strong resistance to various pathogenic microorganisms,especially fungi.With the increasing use of antibiotics,the problems caused by antibiotics,including antibiotic residues and pathogen resistance,are becoming more and more prominent.The research on antimicrobial peptides as new antibiotic substitutes is also a hot spot.This article introduces the action sites and antibacterial mechanisms of several plant antimicrobial peptides,as well as the application of plant antimicrobial peptides in the fields of medicine,agriculture,and food preservation.

Antimicrobial Peptides from the Plants

AMPs （antimicrobial peptides） are small, mostly basic peptides that range in size from 2-9 kDa, and they are an important component of the innate defense system of plants where they are effector molecules considered to be an important defense barrier to pathogens and pests. Nine families of antimicrobial peptides have been identified in plants, including thionins, defensins, lipid transfer proteins, hevein and knotting-like peptides, four cysteine-types, and the recently reported shepherdins, snakins and cyclotides. They are part of both permanent and inducible defense barriers of plants. Transgenic overexpression of the corresponding genes leads to enhanced tolerance to pathogens, and peptide-sensitive pathogen mutants have reduced virulence. In this review, the recent studies on peptides from plant sources, including peptides isolated from indigenous medicine and edible plants of Central-Asia, are briefly discussed with a focus on their origins, antioxidant, antitumor activities and the possible mechanisms of actions in order to provide a profile of important plant peptides.

Type-ll Metacaspases Mediate the processing of Plant Elicitor Peptides in Arabidopsis

Plants can produce animal cytokine-like immune peptides,among which plant elicitor peptides(Peps)derive from the C termini of their precursors(PROPEPs).Recently,the functions of Peps have been expanded beyond plant immunity.However,a long-standing enigma is how PROPEPs are processed into Peps.Here,we report that the Ca2+-dependent type-ll metacaspases(MCs)constitute the proteolytic enzymes to mediate PROPEP processing in Arabidopsis.In protoplasts,co-expression of PROPEP1 with type-ll MCs,including MC4 to MC9,can promote the generation of processed Pep1.Destruction of the catalytic cysteine residue in MC4 or the conserved arginine residue preceding the Pep1 sequence blocks PROPEP1 cleavage,whereas the bacterial elicitor flg22 enhances the MC4-mediated PROPEP1 processing.MC4 cleaves PROPEP1 in vitro and also cleaves PROPEP2 to PROPEP8,but,surprisingly,not PROPEP6 in protoplasts.Domain swapping between PROPEP1 and PROPEP6 suggests a hidden role of the sequence context upstream of the Pep sequence for PROPEP processing.flg22-induced PROPEP1 processing and B otrytis cinerea resistance are severely impaired in the m c4/5/6/7 quadruple-mutant plants.Taken together,our study identifies the type-ll MCs as new players in Pep signaling,and lays the foundation for understanding the regulation of multifaceted functions of Peps in plant immunity and beyond.

Phytomedicines as potential inhibitors of β amyloid aggregation: significance to Alzheimer's disease

Throughout the history of drug development, plants have been an important source for the discovery of novel therapeutically active compounds for many diseases. The ethnopharmacological approach has provided several leads to identify potential new drugs from plant sources, including those for memory disorders. For the treatment of Alzheimer's disease the drug discovery focus shifted from cholinesterase inhibitors, to other targets primarily based on two key neuropathological hallmarks, namely the hyperphosphorylation of the tau protein resulting in the formation of neurofibrillary tangles(NFTs), and the increased formation and aggregation of amyloid-beta peptide(Aβ) derived from amyloid precursor protein(APP). The present article aims to provide a comprehensive literature survey of plants and their constituents that have been tested for Aβ aggregation, thus possibly relieving several features of Alzheimer's disease(AD).