AUTHOR=Zhang Qiong , Zhang Xinmei , Zhuang Rui , Wei Zetong , Shu Weixue , Wang Xiaojie , Kang Zhensheng 

TITLE=TaRac6 Is a Potential Susceptibility Factor by Regulating the ROS Burst Negatively in the Wheat–Puccinia striiformis f. sp. tritici Interaction

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00716

DOI=10.3389/fpls.2020.00716

ISSN=1664-462X

ABSTRACT=<p>Rac/Rop proteins play important roles in the regulation of cell growth and plant defense responses. However, the function of Rac/Rop proteins in wheat remains largely unknown. In this study, a small G protein gene, designated as <italic>TaRac6</italic>, was characterized from wheat (<italic>Triticum aestivum</italic>) in response to <italic>Puccinia striiformis</italic> f. sp. <italic>tritici</italic> (<italic>Pst</italic>) and was found to be highly homologous to the Rac proteins identified in other plant species. Transient expression analyses of the TaRac6-GFP fusion protein in <italic>Nicotiana benthamiana</italic> leaves showed that TaRac6 was localized in the whole cell. Furthermore, transient expression of TaRac6 inhibited Bax-triggered plant cell death (PCD) in <italic>N. benthamiana</italic>. Transcript accumulation of <italic>TaRac6</italic> was increased at 24 h post-inoculation (hpi) in the compatible interaction between wheat and <italic>Pst</italic>, while it was not induced in an incompatible interaction. More importantly, silencing of <italic>TaRac6</italic> by virus induced gene silencing (VIGS) enhanced the resistance of wheat (Suwon 11) to <italic>Pst</italic> (CYR31) by producing fewer uredinia. Histological observations revealed that the hypha growth of <italic>Pst</italic> was markedly inhibited along with more H<sub>2</sub>O<sub>2</sub> generated in the <italic>TaRac6</italic>-silenced leaves in response to <italic>Pst</italic>. Moreover, transcript levels of <italic>TaCAT</italic> were significantly down-regulated, while those of <italic>TaSOD</italic> and <italic>TaNOX</italic> were significantly up-regulated. These results suggest that <italic>TaRac6</italic> functions as a potential susceptibility factor, which negatively regulate the reactive oxygen species (ROS) burst in the wheat–<italic>Pst</italic> interaction.</p>