Yi Cai

Spodoptera litura is a polyphagous lepidopteran pest with rapidly evolving insecticide resistance. Peptide toxins from venomous organisms, many stabilized by the inhibitor cystine knot motif, offer bioinsecticidal potential but show limited oral efficacy. Seven previously reported candidates were recombinantly produced in Pichia pastoris and screened against S. litura by injection and leaf-disc feeding bioassays, followed by whole-plant spray assays. The marine nemertean toxin nemertide α-1, designated A1, showed the strongest oral activity, with a median lethal concentration of 3.97 μg μL⁻¹. Conversely, the engineered spider-venom peptide U1-AGTX-Ta1b R9Q (T1) was most toxic by injection but showed no detectable oral activity, demonstrating that injection toxicity did not predict oral efficacy. High-cell-density fermentation yielded an estimated A1 titer of 1.20 g L⁻¹. Whole-plant foliar application of A1 showed concentration-dependent efficacy. Mortality reached 92.07% at 8 μg μL⁻¹, whereas lower concentrations suppressed larval growth, reducing the mean weight of surviving larvae by 41.55% and 67.58% at 1 and 2 μg μL⁻¹, respectively, and mitigated feeding damage. These findings extend the documented oral insecticidal spectrum of nemertide α-1 to S. litura and demonstrate whole-plant efficacy following foliar application, supporting its development as an active ingredient for foliar-applied peptide bioinsecticides.

Rice blast, caused by Magnaporthe oryzae, poses a serious threat to crop yield; however, immune-active small secreted peptides associated with this disease remain largely uncharacterized. In this study, we identified OsSSIP, a pathogen-inducible peptide in rice. OsSSIP-related similar sequences are widely distributed across angiosperms, while canonical signal peptides appear to be predominantly enriched in Poaceae. Strikingly, the SSP-like homologs of OsSSIP share a conserved N-terminal Tyr-Cys core motif that is essential for OsSSIP activity. Exogenous application of OsSSIP triggered early reactive oxygen species burst, mitogen-activated protein kinase phosphorylation, and defense-related gene expression, while also inhibiting rice root growth. Overexpression of ProOsSSIP enhanced disease resistance accompanied by transient growth suppression, whereas knockout mutants exhibited compromised immunity. A scalable recombinant 5-copy OsSSIP protein produced in Escherichia coli effectively mimicked the native peptide. Both OsSSIP and the recombinant protein elicited immune responses not only in rice and wheat but also in dicots such as tomato, soybean, and Arabidopsis. Furthermore, 2 chemically synthesized peptides derived from nonsignal-peptide similar sequences also displayed immune activity. Collectively, this work demonstrates a previously unappreciated role of OsSSIP in rice immunity against blast disease and highlights the potential of exogenous OsSSIP as an eco-friendly immune stimulator for broad-spectrum crop disease control.

The sustainability of global agricultural systems, a cornerstone for both economic security and food supply chains, is increasingly compromised by phytopat

Phytosulfokine (PSK) is a secreted peptide that plays a pivotal role in regulating plant growth, development, and environmental adaptability. PSK biosynthesis begins with a pre-proprotein precursor that undergoes sulfation by tyrosylprotein sulfotransferase in the cis-Golgi apparatus, followed by proteolytic cleavage by subtilases in the apoplast to yield the mature PSK. This mature peptide is recognized by membrane-bound leucine-rich repeat receptor kinases, known as PSK receptors (PSKRs), which subsequently activate diverse signaling cascades, including cGMP-dependent signaling, phosphorylation events, Ca2+ signaling, mitogen-activated protein kinase pathways, and transcriptional regulation. This review consolidates recent advances in PSK biosynthesis, biological functions, signaling mechanisms, and crosstalk with other plant hormones. By summarizing these insights, we aim to provide a theoretical framework for developing PSK-based strategies to enhance crop resilience and productivity in response to environmental challenges.