The Arabidopsis ubiquitin ligases ATL31 and ATL6 control the defense response as well as the carbon/nitrogen response

In higher plants, the metabolism of carbon (C) and nitrogen nutrients (N) is mutually regulated and referred to as the C and N balance (C/N). Plants are thus able to optimize their growth depending on their cellular C/N status. Arabidopsis and encode a RING-type ubiquitin ligases which play a critical role in the C/N status response (Sato et al. in Plant J 60:852-864, 2009). Since many ATL members are involved in the plant defense response, the present study evaluated whether the C/N response regulators ATL31 and ATL6 are involved in defense responses. Our results confirmed that and expression is up-regulated with the microbe-associated molecular patterns elicitors flg22 and chitin as well as with infections with pv. DC3000 ( DC3000). Moreover, transgenic plants overexpressing and displayed increased resistance to DC3000. In accordance with these data, loss of ATL31 and ATL6 function in an double knockout mutant resulted in reduced resistance to DC3000. In addition, the molecular cross-talk between C/N and the defense response was investigated by mining public databases. The analysis identified the transcription factors MYB51 and WRKY33, which are involved in the defense response, and their transcripts levels correlate closely with and . Further study demonstrated that the expression of , and defense marker genes including and were regulated by C/N conditions. Taken together, these results indicate that ATL31 and ATL6 function as key components of both C/N regulation and the defense response in Arabidopsis.