Histochemical studies of uric acid in some insects. 2. Uric acid and polyphenols in the fat body

Sub-optimal temperatures lead to altered expression of stress-related genes and increased 'Candidatus Liberibacter solanacearum' accumulation in potato psyllid

Introduction

The potato psyllid Bactericera cockerelli is the insect vector of the fastidious bacterium 'Candidatus Liberibacter solanacearum'. The bacterium infects both B. cockerelli and plant species, causing zebra chip (ZC) disease of potato and vein-greening disease of tomato. Temperatures are known to influence the initiation and progression of disease symptom in the host plant, and seasonal transitions from moderate to high temperatures trigger psyllid dispersal migration to facilitate survival.

Methods

'Ca. L. solanacearum' -infected and uninfected psyllids were reared at previously established 'permissible', optimal, and 'non-permissible' and temperatures of 18°C, 24°C, and 30°C, respectively. Gene expression profiles for 'Ca. L. solanacearum'-infected and -uninfected adult psyllids reared at different temperatures were characterized by Illumina RNA-Seq analysis. Bacterial genome copy number was quantified by real-time quantitative-PCR (qPCR) amplification.

Results

Relative gene expression profiles varied in psyllids reared at the three experimental temperatures. Psyllids reared at 18°C and 30°C exhibited greater fold-change increased expression of stress- and 'Ca. L. solanacearum' invasion-related proteins. Quantification by qPCR of bacterial genome copy number revealed that 'Ca. L. solanacearum' accumulation was significantly lower in psyllids reared at 18°C and 30°C, compared to 24°C.

Discussion

Temperature is a key factor in the life history of potato psyllid and multiplication/accumulation of 'Ca. L. solanacearum' in both the plant and psyllid host, influences the expression of genes associated with thermal stress tolerance, among others, and may have been instrumental in driving the co-evolution of the pathosystem.

Protein catabolism in mosquitoes: ureotely and uricotely in larval and imaginal Aedes aegypti

Catabolism of excess dietary protein by Aedes aegypti was investigated during larval development, during and after metamorphosis. Activity profiles were established for xanthine dehydrogenase (XDH, uricotelic pathway) and arginase (ureotelic pathway). Both enzymes are active at all times during the life-cycle. During the aquatic larval and pupal instars, XDH and arginase activities increase with body size. Maximal activities of these two enzyme systems coincide with the time of metamorphic restructuring.Both enzymes are found in the fatbody tissue: XDH activity is found in 80% of the tissue, while arginase activity is distributed equally between abdominal fatbody and the thorax. This might indicate a role for arginase other than catabolic, such as energy metabolism.Arginase activity is high in the aquatic instars and low in sugar-fed females but increases after blood-feeding. XDH activity, also high in larvae and pupae, increases markedly after a blood meal.Larval excretion is characterized by the ureotelic pathway. The pupae as closed systems excrete neither uric acid nor urea; urate accumulates during larval and pupal periods, is conserved throughout metamorphosis, and is finally voided with the meconium by the teneral imago. This presents a form of transient storage-excretion.