AUTHOR=Turrà David , Vitale Stefania , Marra Roberta , Woo Sheridan L. , Lorito Matteo 

TITLE=Heterologous Expression of PKPI and Pin1 Proteinase Inhibitors Enhances Plant Fitness and Broad-Spectrum Resistance to Biotic Threats

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00461

DOI=10.3389/fpls.2020.00461

ISSN=1664-462X

ABSTRACT=<p>Kunitz-type (PKPI) and Potato type I (Pin1) protease inhibitors (PIs) are two families of serine proteinase inhibitors often associated to plant storage organs and with well known insecticidal and nematicidal activities. Noteworthy, their ability to limit fungal and bacterial pathogenesis <italic>in vivo</italic> or to influence plant physiology has not been investigated in detail. To this aim, we generated a set of PVX-based viral constructs to transiently and heterologously express two potato <italic>PKPI</italic> (<italic>PKI1</italic>, <italic>PKI2</italic>) and three potato <italic>Pin1</italic> (<italic>PPI3A2</italic>, <italic>PPI3B2</italic>, <italic>PPI2C4</italic>) genes in <italic>Nicotiana benthamiana</italic> plants, a widely used model for plant-pathogen interaction studies. Interestingly, transgenic plants expressing most of the tested PIs showed to be highly resistant against two economically important necrotrophic fungal pathogens, <italic>Botrytis cinerea</italic> and <italic>Alternaria alternata</italic>. Unexpectedly, overexpression of the <italic>PKI2</italic> Kunitz-type or of the <italic>PPI2C4</italic> and <italic>PPI3A2</italic> Potato type I inhibitor genes also lead to a dramatic reduction in the propagation and symptom development produced by the bacterial pathogen <italic>Pseudomonas syringae</italic>. We further found that localized expression of <italic>PPI2C4</italic> and <italic>PKI2</italic> in <italic>N. benthamiana</italic> leaves caused an increase in cell expansion and proliferation which lead to tissue hypertrophy and trichome accumulation. In line with this, the systemic expression of these proteins resulted in plants with enhanced shoot and root biomass. Collectively, our results indicate that PKPI and Pin1 PIs might represent valuable tools to simultaneously increase plant fitness and broad-spectrum resistance toward phytopathogens.</p>