COS 252-4 - Decrypting seasonal patterns of key pollen genera in Hobart, Australia: a multi-barcode metagenomic approach

Background/Question/Methods

Pollen allergies pose a considerable global public health concern: pollen is a major hay fever trigger and can exacerbate asthma. In this context, pollen monitoring is widely used to support individuals to take preventative measures. As individuals are allergic to specific pollen types, the more specific the information, the more useful for guiding preventative action.

However, routine pollen sampling relies on microscope-based identification, which has limited taxonomic resolution: often to family level. High-throughput DNA sequencing now offers an opportunity to identify mixed pollen samples with greater resolution, in most cases to genus-level.

This study uses high-throughput DNA sequencing to investigate the composition of airborne pollen in Hobart, Tasmania, Australia. We ask: a) What is the genus-level composition of airborne pollen in Hobart? and b) How do the atmospheric concentrations of key pollen taxa change over time?

We collected weekly air samples using a Hirst-Type sampler from December 2018 - October 2020 and sequenced the ITS2 and trnL-trnF barcode regions via Illumina MiSeq. Genera were identified bioinformatically and results were compared with routine microscopic pollen counts.

Results/Conclusions

Both ITS2 and trnL-trnF suggest the grass pollen season is dominated by the temperate grass genera Lolium and Bromus, with subtropical grasses only featured in late summer. Similarly, both markers showed that the introduced Cupressus accounted for 90% of Cupressaceae sequences, while the native Callitris only made up 10%.

Over the three seasons, despite variable season starts, genus dynamics were generally consistent.

These findings have significant implications for public health, environmental monitoring and allergen discovery. Temperate grasses account for the largest burden of allergenic sensitisation in Hobart, and most of southern Australia. Due to urban plantations of Cupressus we expected it to be the most common Cupressaceae pollen, but we were interested to see Callitris contribute. Due to a paucity of research into native Australian aeroallergens, we do not have the diagnostic tools to begin to investigate the allergenic burdens of taxa like Callitris and other pollen that are present in the air.

This dual barcode metagenomic approach revealed key insights into the biodiversity and seasonal patterns of known and potential aeroallergens.