Insight into the α-Amylase Inhibitory Activity of Plant Lipid Transfer Proteins

Organelle Ca2+/CAM1-SELTP confers somatic cell embryogenic competence acquisition and transformation in plant regeneration

Somatic cell totipotency in plant regeneration represents the forefront of the compelling scientific puzzles and one of the most challenging problems in biology. How somatic embryogenic competence is achieved in regeneration remains elusive. Here, we discover uncharacterized organelle-based embryogenic differentiation processes of intracellular acquisition and intercellular transformation, and demonstrate the underlying regulatory system of somatic embryogenesis-associated lipid transfer protein (SELTP) and its interactor calmodulin1 (CAM1) in cotton as the pioneer crop for biotechnology application. The synergistic CAM1 and SELTP exhibit consistent dynamical amyloplast-plasmodesmata (PD) localization patterns but show opposite functional effects. CAM1 inhibits the effect of SELTP to regulate embryogenic differentiation for plant regeneration. It is noteworthy that callus grafting assay reflects intercellular trafficking of CAM1 through PD for embryogenic transformation. This work originally provides insight into the mechanisms responsible for embryogenic competence acquisition and transformation mediated by the Ca2+/CAM1-SELTP regulatory pathway, suggesting a principle for plant regeneration and cell/genetic engineering.

An Effective Plant Small Secretory Peptide Recognition Model Based on Feature Correction Strategy

Plant small secretory peptides (SSPs) play an important role in the regulation of biological processes in plants. Accurately predicting SSPs enables efficient exploration of their functions. Traditional experimental verification methods are very reliable and accurate, but they require expensive equipment and a lot of time. The method of machine learning speeds up the prediction process of SSPs, but the instability of feature extraction will also lead to further limitations of this type of method. Therefore, this paper proposes a new feature-correction-based model for SSP recognition in plants, abbreviated as SE-SSP. The model mainly includes the following three advantages: First, the use of transformer encoders can better reveal implicit features. Second, design a feature correction module suitable for sequences, named 2-D SENET, to adaptively adjust the features to obtain a more robust feature representation. Third, stack multiple linear modules to further dig out the deep information on the sample. At the same time, the training based on a contrastive learning strategy can alleviate the problem of sparse samples. We construct experiments on publicly available data sets, and the results verify that our model shows an excellent performance. The proposed model can be used as a convenient and effective SSP prediction tool in the future. Our data and code are publicly available at https://github.com/wrab12/SE-SSP/.

Structure, Function and Protein Engineering of Cereal-Type Inhibitors Acting on Amylolytic Enzymes

Numerous plants, including cereals, contain seed proteins able to inhibit amylolytic enzymes. Some of these inhibitors, the CM-proteins (soluble in chloroform:methanol mixtures)—also referred to as cereal-type inhibitors (CTIs)—are the topic of this review. CM-proteins were first reported 75 years ago. They are small sulfur-rich proteins of the prolamine superfamily embracing bifunctional α-amylase/trypsin inhibitors (ATIs), α-amylase inhibitors (AIs), limit dextrinase inhibitors (LDIs), and serine protease inhibitors. Phylogenetically CM-proteins are predicted across poaceae genomes and many isoforms are identified in seed proteomes. Their allergenicity and hence adverse effect on humans were recognized early on, as were their roles in plant defense. Generally, CTIs target exogenous digestive enzymes from insects and mammals. Notably, by contrast LDI regulates activity of the endogenous starch debranching enzyme, limit dextrinase, during cereal seed germination. CM-proteins are four-helix bundle proteins and form enzyme complexes adopting extraordinarily versatile binding modes involving the N-terminal and different loop regions. A number of these inhibitors have been characterized in detail and here focus will be on target enzyme specificity, molecular recognition, forces and mechanisms of binding as well as on three-dimensional structures of CM-protein–enzyme complexes. Lastly, prospects for CM-protein exploitation, rational engineering and biotechnological applications will be discussed.

Lipid Transfer Proteins (LTPs)-Structure, Diversity and Roles beyond Antimicrobial Activity

Lipid transfer proteins (LTPs) are among the most promising plant-exclusive antimicrobial peptides (AMPs). They figure among the most challenging AMPs from the point of view of their structural diversity, functions and biotechnological applications. This review presents a current picture of the LTP research, addressing not only their structural, evolutionary and further predicted functional aspects. Traditionally, LTPs have been identified by their direct isolation by biochemical techniques, whereas omics data and bioinformatics deserve special attention for their potential to bring new insights. In this context, new possible functions have been identified revealing that LTPs are actually multipurpose, with many additional predicted roles. Despite some challenges due to the toxicity and allergenicity of LTPs, a systematic review and search in patent databases, indicate promising perspectives for the biotechnological use of LTPs in human health and also plant defense.

Biotechnological applications of versatile plant lipid transfer proteins (LTPs)

Plant AMPs are usually cysteine-rich, and can be classified in several classes, including lipid transfer proteins (LTPs). LTPs are small plant cationic peptides, and can be classified in two subclasses, LTP₁ (9-10 kDa) and LTP₂ (7 kDa). They have been identified and isolated from various plant species and can be involved in a number of processes, including responses against several phytopathogens. LTP₁ presents 4 parallel α- helices and a 3₁₀-helix fragment. These structures form a tunnel with large and small entrances. LTP₂ presents 3 parallel α- helices, which form a cavity with triangular structure. Both LTP subclasses present a hydrophobic cavity, which makes interaction with different lipids and general hydrophobic molecules possible. Several studies report a broad spectrum of activity of plant LTPs, including antibacterial, antifungal, antiviral, antitumoral, and insecticidal activity. Thus, these molecules can be employed in human and animal health as an alternative to the conventional treatment of disease, well as providing the source of novel drugs. However, employing peptides in human health can present challenges, such as the toxicity of peptides, the difference between the results found in in vitro assays and in pre-clinical or clinical tests and their low efficiency against Gram-negative bacteria. In this context, plant LTPs can be an interesting alternative means by which to bypass such challenges. This review addresses the versatility of plant LTPs, their broad spectrum of activities and their potential applications in human and animal health and in agricultural production, and examines challenges in their biotechnological application.

Bifunctional Inhibitors from Capsicum chinense Seeds with Antimicrobial Activity and Specific Mechanism of Action Against Phytopathogenic Fungi

BACKGROUND

Antimicrobial peptides (AMPs) are found in the defense system in virtually all life forms, being present in many, if not all, plant species.

OBJECTIVE

The present work evaluated the antimicrobial, enzymatic activity and mechanism of action of the PEF2 fraction from Capsicum chinense Jack. seeds against phytopathogenic fungi.

METHODS

Peptides were extracted from C. chinense seeds and subjected to reverse-phase chromatography on an HPLC system using a C18 column coupled to a C8 guard column, then the obtained PEF2 fraction was rechromatographed using a C2/C18 column. Two fractions, named PEF2A and PEF2B, were obtained. The fractions were tested for antimicrobial activity on Colletotrichum gloeosporioides, Colletotrichum lindemuthianum, Fusarium oxysporum and Fusarium solani. Trypsin inhibition assays, reverse zymographic detection of protease inhibition and α-amylase activity assays were also performed. The mechanism of action by which PEF2 acts on filamentous fungi was studied through analysis of membrane permeability and production of reactive oxygen species (ROS). Additionally, we investigated mitochondrial functionality and caspase activation in fungal cells.

RESULTS

It is possible to observe that PEF2 significantly inhibited trypsin activity and T. molitor larval α-amylase activity. The PEF2 fraction was able to inhibit the growth of C. gloeosporioides, C. lindemuthianum and F. oxysporum. PEF2A inhibited the growth of C. lindemuthianum (75%) and F. solani (43%). PEF2B inhibited C. lindemuthianum growth (66%) and F. solani (94%). PEF2 permeabilized F. solani cell membranes and induced ROS in F. oxysporum and F. solani. PEF2 could dissipate mitochondrial membrane potential but did not cause the activation of caspases in all studied fungi.

CONCLUSION

The results may contribute to the biotechnological application of these AMPs in the control of pathogenic microorganisms in plants of agronomic importance.