Metabolic profiling reveals local and systemic responses of kiwifruit to
Pseudomonas syringae pv. actinidiae
Abstract
Pseudomonas syringae pv. actinidiae (Psa), a bacterial pathogen, causes
bacterial canker disease in kiwifruit. To elucidate the local and
systemic influences of Psa infection on kiwifruit, comprehensive
analyses were conducted by combining metabolomic and physiological
approach under Psa-infected treatment and control in leaves, stems and
bleeding saps. Our results show that Psa infection stimulated kiwifruit
metabolic reprogramming. Levels of sugars, fumarate, and malic acid were
decreased in Psa-infected leaves and stems, accompanied by the increased
level of amino acids (AAs), which is associated with energy metabolism
and defense metabolism. Arg, Gln, and pyroglutamic acid systematically
were accumulated in long-distance leaves, which probably confers to
systemic acquired resistance (SAR). In situ zymography analysis showed
that Psa-infection increased N-acetyl-glucosaminidases (chitinases)
activity and was highest at the root tips, indicating Psa- inoculation
accelerated the nitrogen (N) cycling in kiwifruit. Moreover, phenolic
compounds were negatively and lignin was positively related to kiwifruit
Psa-resistance, respectively. Our results first reveal that Psa enhances
infection by manipulating carbon (C)/N metabolism and sweet immunity,
and that host lignin synthesis is a major physical barrier for
restricting bacterial infection. This study provides an insight into the
complex remodeling of plant metabolic response to Psa stress.