Environmental Factors Variably Impact Tea Secondary Metabolites in the Context of Climate Change.

Climate change is impacting food and beverage crops around the world with implications for environmental and human well-being. While numerous studies have examined climate change effects on crop yields, relatively few studies have examined effects on crop quality (concentrations of nutrients, minerals, and secondary metabolites). This review article employs a culturally relevant beverage crop, tea (Camelia sinensis), as a lens to examine environmental effects linked to climate change on the directionality of crop quality. Our systematic review identified 86 articles as relevant to the review question. Findings provide evidence that shifts in seasonality, water stress, geography, light factors, altitude, herbivory and microbes, temperature, and soil factors that are linked to climate change can result in both increases and decreases up to 50% in secondary metabolites. A gap was found regarding evidence on the direct effects of carbon dioxide on tea quality, highlighting a critical research area for future study. While this systematic review provides evidence that multiple environmental parameters are impacting tea quality, the directionality and magnitude of these impacts is not clear with contradictory evidence between studies likely due to confounding factors including variation in tea variety, cultivar, specific environmental and agricultural management conditions, and differences in research methods. The environmental factors with the most consistent evidence in this systematic review were seasonality and water stress with 14 out of 18 studies (78%) demonstrating a decrease in concentrations of phenolic compounds or their bioactivity with a seasonal shift from the spring and /or first tea harvest to other seasons and seven out of 10 studies (70%) showing an increase in levels of phenolic compounds or their bioactivity with drought stress. Herbivory and soil fertility were two of the variables that showed the greatest contradictory evidence on tea quality. Both herbivory and soil fertility are variables which farmers have the greatest control over, pointing to the importance of agricultural management for climate mitigation and adaptation. The development of evidence-based management strategies and crop breeding programs for resilient cultivars are called for to mitigate climate impacts on crop quality and overall risk in agricultural and food systems.

Inhibition of the SAPK/JNK pathway blocks the stimulatory effects of glutamine on fluid secretion by the Malpighian tubules of Rhodnius prolixus.

Physiological levels of amino acids such as glutamine, glutamate, aspartate and proline increase the rates of fluid secretion and ion transport by serotonin-stimulated Malpighian tubules (MTs) of Rhodnius prolixus. Here, we examine the proposal that the effects of glutamine are mediated through activation of specific kinases to produce the observed increases in fluid secretion. The glutamine-dependent increase in MT fluid secretion rate was blocked by two chemically unrelated inhibitors of the stress activated protein kinase (SAPK) pathway, SP600125 and dicumarol. Inhibitors of phosphatidyl inositol-3 kinase, p38 mitogen activated protein kinase (MAPK), extracellular-signal regulated kinases and MAPK kinase did not block glutamine's effects on fluid secretion rate when applied at commonly used concentrations. Inhibitors of protein kinase A or C reduced fluid secretion rates of serotonin-stimulated MTs, but did not block the response to glutamine. The glutamine-dependent increase in fluid secretion was also insensitive to cytoskeletal disrupting agents and protein synthesis inhibitors. Results of this study are the first to suggest a role for the SAPK pathway in the control of fluid secretion rates by insect MTs.

Amino acids modulate ion transport and fluid secretion by insect Malpighian tubules.

Insect haemolymph typically contains very high levels of free amino acids. This study shows that amino acids can modulate the secretion of ions and water by isolated Malpighian tubules of Rhodnius prolixus and Drosophila melanogaster. Secretion rates of Rhodnius tubules in amino-acid-free saline increase after addition of serotonin to a peak value, then slowly decline to a plateau. Addition of glutamine, glutamate or aspartate to such tubules increases secretion rates dramatically relative to the controls in amino-acid-free saline, and these increases are sustained for 1-2 h. Seven other amino acids have more modest stimulatory effects, whereas lysine and arginine are inhibitory. Secreted fluid pH and Na(+) concentration increase and K(+) concentration decreases in response to glutamine. Pre-incubation of unstimulated tubules in saline solutions containing amino acids followed by stimulation with serotonin in amino-acid-free saline shows that the effects of amino acids far outlast the duration of exposure to them. Amino acids do not appear to be important as metabolites in Rhodnius tubules, nor do they act to draw significant amounts of water into the lumen by osmosis. Significant stimulation of fluid secretion can be achieved by physiological levels of particular amino acids, whereas those amino acids that inhibit fluid secretion only do so at concentrations much above those at which they occur naturally in the haemolymph. Secretion rates of unstimulated or stimulated Drosophila tubules are increased by pre-incubation in saline solutions containing glutamine or methionine or by continuous exposure to glutamine, methionine or tyrosine. Cysteine dramatically inhibited fluid secretion by Drosophila tubules, but only at concentrations well above the physiological range. We suggest that the amino acids probably function as compatible intracellular osmolytes that are necessary for sustained secretion at high rates by the Malpighian tubules.