Molecular analysis confirms the long-distance transport of Juniperus ashei pollen

Abstract

Although considered rare, airborne pollen can be deposited far from its place of origin under a confluence of favorable conditions. Temporally anomalous records of Cupressacean pollen collected from January air samples in London, Ontario, Canada have been cited as a new case of long-distance transport. Data on pollination season implicated Juniperus ashei (mountain cedar), with populations in central Texas and south central Oklahoma, as the nearest source of the Cupressacean pollen in the Canadian air samples. This finding is of special significance given the allergenicity of mountain cedar pollen. While microscopy is used extensively to identify particles in the air spora, pollen from all members of the Cupressaceae, including Juniperus, are morphologically indistinguishable. Consequently, we implemented a molecular approach to characterize Juniperus pollen using PCR in order to test the long-distance transport hypothesis. Our PCR results using species-specific primers confirmed that the anomalous Cupressacean pollen collected in Canada was from J. ashei. Forward trajectory analysis from source areas in Texas and the Arbuckle Mountains in Oklahoma and backward trajectory analysis from the destination area near London, Ontario were completed using models implemented in HYSPLIT4 (Hybrid Single-Particle Lagrangian Integrated Trajectory). Results from these trajectory analyses strongly supported the conclusion that the J. ashei pollen detected in Canada had its origins in Texas or Oklahoma. The results from the molecular findings are significant as they provide a new method to confirm the long-distance transport of pollen that bears allergenic importance.

Fig 1. Juniperus ashei distribution map in United States.

Fig 2

(2A) Agarose gel electrophoresis of PCR products from amplification experiments with Juniperus pollen DNA tested with species-specific J. ashei primers (asheimatKF1 and asheimatKR1). Lane 1: Juniperus ashei pollen DNA, Lane 2: Juniperus pinchotii pollen DNA, Lane 3: Juniperus virginiana pollen DNA, Lane 4: Blank, Lane 5: Negative control, Lane 6: λ-DNA ladder (HindIII) as marker (M). (2B) Agarose gel electrophoresis of PCR products obtained from the DNA extracted from the Buck bio-slide sampler from Canada on 15 January 2014 and tested with the primers asheimatKF1 and asheimatKR1. Lane 1: Blank (No DNA), Lane 2: Juniperus ashei pollen DNA obtained from Canada slide on 15 January 2014, Lane 3: Blank (No DNA), Lane 4: Positive control, Lane 5: Negative control (only milliQ water and no DNA), Lane 6–7: Blank (No DNA), Lane 8: exACTGene^™ mid- range (300-5000bp) DNA Ladder.

Fig 3. Forward trajectories used in the analysis.

(3A) Forward trajectories from Austin, Texas on 12 January 2014 which pass over Tulsa and London, (3B) Forward matrix trajectories from Austin, Texas on 12 January 2014 which pass over Tulsa and London, (3C) Forward trajectories from Arbuckle Mountains, Oklahoma on 12 January 2014, which pass over Tulsa and London.

Fig 4. Backward trajectories from London, Ontario, Canada which pass over Arbuckle Mountains, Oklahoma and Austin, Texas.

Fig 5. Juniperus ashei pollen registered from the Tulsa atmosphere on 12 January 2014 observed under a light microscope.