Overexpression of four Arabidopsis thaliana NHL genes in soybean (Glycine max) roots and their effect on resistance to the soybean cyst nematode (Heterodera glycines)

• Four Arabidopsis thaliana NHL genes were overexpressed in soybean roots.
• Overexpression of NHL1 and NHL8 reduced soybean cyst nematode population ∼50%.
• NHL1 is most similar to NDR1, and NHL8 is an E3 ubiquitin ligase.
• PR gene expression in NHL1 and NHL8 roots shows upregulation of JA and ET.
• The mechanism by which they act in soybean might differ from that of Arabidopsis.

Glycine max is one of the most important cash-crops in the US. Major losses in soybean production are reported annually due to the attack of the soybean cyst nematode (Heterodera glycines). Since chemical control is neither environmental nor economically viable, efforts have been focused on enhancing the plants defense system. Plants have developed mechanisms to identify and react to pathogen attack. Basal defenses are activated by resistance (R) proteins. The Arabidopsis NON-RACE-SPECIFIC DISEASE RESISTANCE 1, NDR1 protein shows some sequence similarity to the tobacco HAIRPIN INDUCED GENE 1 (HIN1), is localized to the plasma membrane, and usually interacts with CC-NB-LRR R proteins to mediate defense signaling. Forty five NDR1/HIN1-LIKE (NHL) genes have been found in Arabidopsis. Four of them were overexpressed in soybean roots to determine if they could confer resistance to H. glycines. AtNHL1 and AtNHL8 significantly decreased the number of mature females to 50 and 46% of the number found in control roots. Relative expression analysis showed they induced the expression of marker genes for jasmonic acid (PR3 and OSM, encoding chitinase B and an osmotin, respectively) and ethylene (EBF, ERF1, and ERS2, encoding the EIN3-binding F box protein, the ethylene response factor 1, and the ethylene response sensor 2, respectively). NHL1 is most similar to NDR1, and NHL8 is an E3 ubiquitin ligase, Ariadne ring zinc finger protein. Our observations confirm the role of NHL1 and NHL8 in the plant defense mechanism against pathogens observed in Arabidopsis, by conferring resistance to SCN in soybean.