AUTHOR=Kou Xiaobing , Liu Qian , Sun Yangyang , Wang Peng , Zhang Shaoling , Wu Juyou 

TITLE=The Peptide PbrPSK2 From Phytosulfokine Family Induces Reactive Oxygen Species (ROS) Production to Regulate Pear Pollen Tube Growth

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.601993

DOI=10.3389/fpls.2020.601993

ISSN=1664-462X

ABSTRACT=<p>Phytosulfokines (PSKs) are plant peptide growth factors that participate in multiple biological processes, including cell elongation and immune signaling. However, little is known about PSKs in Rosaceae species. Here, we identified 10 <italic>PSK</italic> genes in pear (<italic>Pyrus bretschneideri</italic>), 11 in apple (<italic>Malus</italic> × <italic>domestica</italic>), four in peach (<italic>Prunus persica</italic>), six in strawberry (<italic>Fragaria vesca</italic>), and five in Chinese plum (<italic>Prunus mume</italic>). In addition, we undertook comparative analysis of the <italic>PSK</italic> gene family in pear and the four other species. Evolutionary analysis indicated that whole genome duplication events (WGD) may have contributed to the expansion of the <italic>PSK</italic> gene family in Rosaceae. Transcriptomes, reverse transcription-PCR and quantitative real-time-PCR analyses were undertaken to demonstrate that <italic>PbrPSK2</italic> is highly expressed in pear pollen. In addition, by adding purified <italic>E. coli</italic>-expressed PbrPSK2 to pollen and using an antisense oligonucleotide approach, we showed that PbrPSK2 can promote pear pollen tube elongation in a dose-dependent manner. Furthermore, PbrPSK2 was found to mediate the production of reactive oxygen species to regulate pear pollen tube growth.</p>