Cork oak is an economically important forest species showing a great tolerance to high temperatures and shortage of water. However, the mechanisms underlying this plasticity are still poorly understood. Among the stress regulators, transcription factors (TFs) are especially important since they can control a wide range of stress-inducible genes, which make them powerful targets for genetic engineering of stress tolerance. Here we evaluated the influence of increasing temperatures (up to 55 °C) or drought (18% field capacity, FC) on the expression profile of an R2R3-MYB transcription factor of cork oak, the QsMYB1. QsMYB1 was previously identified as being preferentially expressed in cork tissues and as having an associated alternative splicing mechanism, which results in two different transcripts (QsMYB1.1 and QsMYB1.2). Expression analysis by reverse transcription quantitative PCR (RT-qPCR) revealed that increasing temperatures led to a gradual down-regulation of QsMYB1 transcripts with more effect on QsMYB1.1 abundance. On the other hand, under drought condition, expression of QsMYB1 variants, mainly the QsMYB1.2, was transiently up-regulated shortly after the stress imposition. Recovery from each stress has also resulted in a differential response by both QsMYB1 transcripts. Several physiological and biochemical parameters (plant water status, chlorophyll fluorescence, lipid peroxidation and proline content) were determined in order to monitor the plant performance under stress and recovery. In conclusion, this report provides the first evidence that QsMYB1 TF may have a putative function in the regulatory network of cork oak response to heat and drought stresses and during plant recovery.
Keywords: 5′-untranslated region; 5′UTR; Abiotic stress; Cork oak; DW; F; F(0); F(m); F(v); F(v)/F(m); FC; FW; Gene expression; MDA; R2R3-MYB; RT-qPCR; RWC; Recovery; TFs; TW; WS; WW; dry weight; field capacity; gDNA; genomic DNA; malondialdehyde; maximum fluorescence; maximum quantum yield of PSII photochemistry; minimum fluorescence; quantum yield of PSII photochemistry; relative water content; reverse transcription quantitative PCR; steady state fluorescence; tissue fresh weight; transcription factors; turgid weight; variable fluorescence; water stress; well watered; Ф(PSII).
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