Transcriptome analysis provides insights into the delayed sticky disease symptoms in Carica papaya.

KEY MESSAGE: Global gene expression analysis indicates host stress responses, mainly those mediated by SA, associated to the tolerance to sticky disease symptoms at pre-flowering stage in Carica papaya. Carica papaya plants develop the papaya sticky disease (PSD) as a result of the combined infection of papaya meleira virus (PMeV) and papaya meleira virus 2 (PMeV2), or PMeV complex. PSD symptoms appear only after C. papaya flowers. To understand the mechanisms involved in this phenomenon, the global gene expression patterns of PMeV complex-infected C. papaya at pre-and post-flowering stages were assessed by RNA-Seq. The result was 633 and 88 differentially expressed genes at pre- and post-flowering stages, respectively. At pre-flowering stage, genes related to stress and transport were up-regulated while metabolism-related genes were down-regulated. It was observed that induction of several salicylic acid (SA)-activated genes, including PR1, PR2, PR5, WRKY transcription factors, ROS and callose genes, suggesting SA signaling involvement in the delayed symptoms. In fact, pre-flowering C. papaya treated with exogenous SA showed a tendency to decrease the PMeV and PMeV2 loads when compared to control plants. However, pre-flowering C. papaya also accumulated transcripts encoding a NPR1-inhibitor (NPR1-I/NIM1-I) candidate, genes coding for UDP-glucosyltransferases (UGTs) and several genes involved with ethylene pathway, known to be negative regulators of SA signaling. At post-flowering, when PSD symptoms appeared, the down-regulation of PR-1 encoding gene and the induction of BSMT1 and JA metabolism-related genes were observed. Hence, SA signaling likely operates at the pre-flowering stage of PMeV complex-infected C. papaya inhibiting the development of PSD symptoms, but the induction of its negative regulators prevents the full-scale and long-lasting tolerance.

Within patient genetic diversity of blaKPC harboring Klebsiella pneumoniae in a Colombian hospital and identification of a new NTEKPC platform.

Resistance to carbapenems in Klebsiella pneumoniae has been mostly related with the worldwide dissemination of KPC, largely due to the pandemic clones belonging to the complex clonal (CC) 258. To unravel blaKPC post-endemic clinical impact, here we describe clinical characteristics of 68 patients from a high complexity hospital, and the molecular and genetic characteristics of their 139 blaKPC-K. pneumoniae (KPC-Kp) isolates. Of the 26 patients that presented relapses or reinfections, 16 had changes in the resistance profiles of the isolates recovered from the recurrent episodes. In respect to the genetic diversity of KPC-Kp isolates, PFGE revealed 45 different clonal complexes (CC). MLST for 12 representative clones showed ST258 was present in the most frequent CC (23.0%), however, remaining 11 representative clones belonged to non-CC258 STs (77.0%). Interestingly, 16 patients presented within-patient genetic diversity of KPC-Kp clones. In one of these, three unrelated KPC-Kp clones (ST258, ST504, and ST846) and a blaKPC-K. variicola isolate (ST182) were identified. For this patient, complete genome sequence of one representative isolate of each clone was determined. In K. pneumoniae isolates blaKPC was mobilized by two Tn3-like unrelated platforms: Tn4401b (ST258) and Tn6454 (ST504 and ST846), a new NTEKPC-IIe transposon for first time characterized also determined in the K. variicola isolate of this study. Genome analysis showed these transposons were harbored in different unrelated but previously reported plasmids and in the chromosome of a K. pneumoniae (for Tn4401b). In conclusion, in the blaKPC post-endemic dissemination in Colombia, different KPC-Kp clones (mostly non-CC258) have emerged due to integration of the single blaKPC gene in new genetic platforms. This work also shows the intra-patient resistant and genetic diversity of KPC-Kp isolates. This circulation dynamic could impact the effectiveness of long-term treatments.