Overexpression of PSK-γ in Arabidopsis promotes growth without influencing pattern-triggered immunity

Phytosulfokine-α (PSK-α) is a disulfated pentapeptide with the sequence YIYTQ. As a new peptide hormone, PSK-α promotes plant growth and development but represses pattern-triggered immunity (PTI) against bacterial pathogens. Our recent study identified a novel phytosulfokine, PSK-γ, from soybean. The sequence of PSK-γ is YVYTQ in which the tyrosines are sulfated. Expression of PSK-γ significantly increased seed size and weight in transgenic plants by inducing embryo cell expansion. In this study, we further found that the constitutive expression of PSK-γ in Arabidopsis promotes the growth of vegetative organs as well as seeds. Moreover, overexpressed PSK-γ does not influence plant PTI against bacterial pathogens. These findings demonstrate a potential use of PSK-γ in genetic improvement of crop growth and yield by molecular breeding.