Rhizobium rhizogenes rolC gene promotes leaf senescence and enhances osmotic stress resistance in Arabidopsis: the positive role of abscisic acid

The root oncogenic loci (rol) C oncogene has been identified as a key player during the plant-Rhizobium rhizogenes interaction and is considered to confer resistance to plant abiotic stresses, yet the underlying mechanisms remain largely elusive. In this study, Arabidopsis plants constitutively overexpressing rolC were produced. Biometric analysis showed that rolC induced diverse phenotypic modifications, including dwarfism, increased number of stem branches (1.3 times more than WT), weak root growth, early flowering (1.6 days earlier than WT) and premature leaf senescence. In addition, senescence stimulus (exogenous ethylene: 10 or 100 mu L L-1) and 10% (w/v) polyethylene glycol 6000 (PEG) treatments demonstrated that rolC mediated leaf abscisic acid (ABA) enhancement in Arabidopsis, and this might be involved in rolC-induced premature leaf senescence and resistance enhancement to osmotic stress. It is concluded that rolC-induced premature leaf senescence may be involved in an abiotic stress escape mechanism in Arabidopsis, which is closely related to the increase of endogenous ABA levels. These findings provide new insights into the role of rolC in plant-bacterial interaction and uncover the potential of biotechnological application associated with R. rhizogenes/rol genes in plant drought defense.