GmSHMT08 ‐Mediated Soybean Cyst Nematode Resistance Is Negatively Modulated by Two Heat Shock Protein 70s in Soybean

ABSTRACT The soybean GmSHMT08 ( Rhg4 ) is a major gene conferring resistance to soybean cyst nematode (SCN), which is a devastating pathogen in soybean, yet its underlying resistance mechanism remains elusive. Heat shock protein 70 (HSP70) mainly functions in maintaining protein homoeostasis and regulating plant immunity. In this study, CRISPR/Cas9‐mediated knockout of two highly similar GmHSP70s [ GmHSP70‐13a ( Glyma.13g254900 ) and GmHSP70‐15a ( Glyma.15g059900 )] enhanced, whereas overexpressing either of them suppressed, SCN resistance. Both GmHSP70‐13a and GmHSP70‐15a interacted with the key one‐carbon metabolism enzyme GmSHMT08, and promoted GmSHMT08 degradation via 26S proteasome pathway, but neither of them altered GmSHMT08 transcript levels in soybean. Furthermore, both GmHSP70‐13a and GmHSP70‐15a were strongly induced in susceptible soybeans, while both of them still remained low in resistant soybeans, after SCN infection. Taken together, GmSHMT08 ‐mediated SCN resistance is shown to be negatively modulated by both GmHSP70‐13a and GmHSP70‐15a. The regulation is facilitated through interacting with and influencing 26S proteasome system‐involved degradation of GmSHMT08. This study elucidates a SCN‐resistance mechanism of GmSHMT08 , expands functions of HSP70s and provides two GmHSP70s gene‐editing targets for soybean SCN resistance breeding.