Gene expression changes in response to drought stress in Ilex paraguariensis leaves

Abstract

Ilex paraguariensis St. Hil. is recognized as a shade-tolerant tree, cultivated in north-eastern Argentina, south-eastern Brazil, and Paraguay. Its leaves and young shoots are industrialised and; hence, being used to prepare a traditional tea-like infusion (mate-tea) with various medicinal benefits. Under the prevailing agro-climatic conditions in NE Argentina and with the occurrence of high temperatures and scarce rains during spring or summer, I. paraguariensis plants are subjected to water stress, reducing their yield. Differential Display was used to compare differences in gene expression between stressed and unstressed (control) potted plants. We found 52 differentially expressed transcripts (DETs), analysing banding patterns of Differential Display polyacrylamide gels, in which 38 DETs were induced, and 14 DETs were repressed in response to drought. Sequence comparisons revealed that 19% of the fragments showed no homologies, whereas 40.5 % of the total number of fragments had strong similarities with database entries of known functions. The other DETs belonged to unclassified proteins or genes with unknown functions. Interestingly, 12% of the DNA sequences were related to signal transduction, and 2% of the sequences were identified as transcription factors. Approximately, 12% of the annotated sequences were involved in stress tolerance and metal homeostasis, while 7% of the DETs were associated with photosynthesis. Other groups, representing 12%, included those involved in secondary metabolism, lignin biosynthesis, cell walls and RNA stabilization/chaperone activity. When integrated with physiological data, our results suggest that the transcriptional activity of some of the studied genes could be related to the degree of drought tolerance/susceptibility of I. paraguariensis.

Growth and Physiological Responses of Yerba Mate Seedlings and Mini-Cuttings Under Drought Stress

“…paraguariensis plants are sensitive to water deficits, negatively affecting growth (height and biomass accumulation) because of a decreased photosynthetic capacity (lowers photosynthetic rate, chlorophyll content, stomatal conductance, leaf number and leaf area). During the annual growth cycle, plantations are subject to periods of water deficits and high temperatures in spring and summer, which negatively affect yields (Acevedo et al, 2016). In our experiment, the different type of plants tested (seedlings and mini-cuttings), showed a lower total height proportional to the stress level, being 7 % and 15 % for plants subjected to drought stress in treatments D1 and D2 respectively ( Figure 3B).…”

“…When trees are under drought stress situations, a decrease in stomatal conductance and photosynthetic activity occurs (Chen, 2020), resulting in a lower total dry weight, decrease in leaf area, loss of leaves or even total defoliation (Monclus et al, 2006). The yerba mate plant is very sensitive to drought stress, negatively affecting its growth and yield per hectare (Acevedo et al, 2016). This is because stomatal conductance and net photosynthesis are affected by drought stress situations (Acevedo et al, 2013; and can lead to decreases in leaf area and dry weight of plants (Sansberro et al, 2004).…”

Assessment of reference genes for real-time quantitative PCR normalization in Ilex paraguariensis leaves during drought

“…The stress response and acclimatization of plants to water deficit cause a complex readjustment in the expression of a large number of genes (Shinozaki andYamaguchi-Shinozaki 2007, Singh andLaxmi 2015). The isolation and characterization of these genes constitute a reliable way to understand the mechanisms underlying water stress (Acevedo et al 2016). To quantify the expression of a particular gene, reverse transcription of RNA followed by real-time PCR quantitative (qPCR) is the most commonly used approach because of its high sensitivity, specificity, and large dynamic range (Gutierrez et al 2008).…”

Transcript and metabolic adjustments triggered by drought in Ilex paraguariensis leaves

“…Although the physiological responses to water deficit are underpinned by reprogramming of the metabolism and gene expression, these protective mechanisms are still far from full characterized in yerba mate and their clarification is necessary to better understand the acclimation process to drought conditions. In this way, we observed a limited number of differentially expressed transcripts (DETs) using mRNA differential display to associate the expression profile of stressed and unstressed plants (Acevedo et al 2016). We identified 62 DETs of which only 40.5% had strong similarities with database entries of known functions, while the others belonged to unclassified proteins or genes with no assigned functions.…”