The potyviral protein 6K2 from Turnip mosaic virus increases plant resilience to drought

Abstract

Drought is a major cause of yield loss for crops worldwide. Climate change is predicted to increase global crop losses due to drought through rising temperature and decreased water availability. Virus infection can increase drought tolerance of infected plants compared to non-infected plants; however, the mechanisms mediating virus-induced drought tolerance remain unclear. In this study, we demonstrate Turnip mosaic virus (TuMV) infection increases Arabidopsis thaliana survival under drought compared to uninfected plants. To determine if specific TuMV proteins mediate drought tolerance, we cloned the coding sequence for each of the major viral proteins and generated transgenic A. thaliana that constitutively express each protein. Three TuMV proteins, 6K1, 6K2, and NIa-Pro, enhanced drought tolerance of A. thaliana when expressed constitutively in plants compared to controls. Expression of 6K2 also increased plant biomass relative to controls, but had no impact on root biomass, trichome numbers, or on the number of stomata. While drought induced transcripts related to abscisic acid (ABA) biosynthesis and ABA levels in control plants, compared to under well-watered conditions, there were no changes in ABA or related transcripts in plants expressing 6K2 under drought conditions compared to well-watered. 6K2 expression also conveyed drought tolerance in another host plant, Nicotiana benthamiana, when expressed using a virus over expression construct derived from Foxtail mosaic virus (FoMV). Although the exact mechanisms are still unknown, these results suggest 6K2-induced drought tolerance is ABA-independent and that plant viruses may represent novel sources of drought tolerance for crop plants.

Exploiting Virus Infection to Protect Plants from Abiotic Stresses: Tomato Protection by a Begomovirus

“…The first descriptions of a virus-dependent increase in plant tolerance to drought concerned RNA viruses such as BMV, CMV, TMV, and TRV [ 8 ]. PVX and PPV were also described to be beneficial for N. benthamiana and Arabidopsis grown under drought conditions [ 9 ]. The ability of TYLCV, particularly of its C4 protein, to promote enhanced tolerance to drought was reported in tomato and in N. benthamiana ; however, a mechanism explaining this phenomenon was not proposed [ 13 ].…”

“…These results were unexpected, because ABA is the key hormone regulating plant responses to drought [ 5 ], while SA is induced in response to infections by pathogens [ 6 , 7 ]. However, the establishment of drought tolerance in an ABA-independent manner was also shown in transgenic Arabidopsis expressing the tomato yellow leaf curl C4 gene [ 8 ] or the turnip mosaic virus (TuMV) 6K2 gene [ 9 ]. TRV was shown to promote plant tolerance to low temperature [ 10 ], and PVX to environmental oxidation [ 11 ].…”