Abstract
Abscisic acid (ABA) is known to play roles in regulating plant tolerance to various abiotic stresses, but whether ABA’s effects on heat tolerance are associated with its regulation of heat stress transcription factors (HSFs) and heat shock proteins (HSPs) is not well documented. The objective of this study was to determine whether improved heat tolerance of tall fescue (Festuca arundinacea Schreb.) by ABA was through the regulation of HSFs and HSPs. ABA-responsive transcriptional factors, ABA-responsive element binding protein 3 (FaAREB3) and dehydration-responsive element binding protein 2A (FaDREB2A) of tall fescue, were able to bind to the cis-elements in the promoter of tall fescue heat stress transcription factor A2c (FaHSFA2c). Exogenous ABA (5 μM) application enhanced heat tolerance of tall fescue, as manifested by increased leaf photochemical efficiency and membrane stability under heat stress (37/32 °C, day/night). The expression levels of FaHSFA2c, several tall fescue HSPs (FaHSPs), and ABA-responsive transcriptional factors were up-regulated in plants treated with ABA. Deficiency of Arabidopsis heat stress transcription factor A2 (AtHSFA2) suppressed ABA-induction of AtHSPs expression and ABA-improved heat tolerance in Arabidopsis. These results suggested that HSFA2 plays an important role in ABA-mediated plant heat tolerance, and FaAREB3 and FaDREB2A may function as upstream trans-acting factors and regulate transcriptional activity of FaHSFA2c and the downstream FaHSPs, leading to improved heat tolerance.
Highlights
Abscisic acid (ABA) is known to play important roles in regulating plant responses to various abiotic stresses, especially those stresses involving dehydration, such as drought, salinity, and cold stress [1]
ABA-Responsive Factors of Tall Fescue Binding to Cis-Elements in FaHSFA2c Promoter
The expression levels of FaHSFA2c, several FaHSPs, and ABA-responsive transcriptional factors were up-regulated in tall fescue plants with ABA treatment under heat stress
Summary
Abscisic acid (ABA) is known to play important roles in regulating plant responses to various abiotic stresses, especially those stresses involving dehydration, such as drought, salinity, and cold stress [1]. Some studies have reported improved heat tolerance with ABA through exogenous application or manipulation of ABA-related genes [2,3,4]. Both ABA biosynthesis mutants (aba mutants) and ABA-insensitive mutants (abi and 2) showed defects in heat stress tolerance [5]. ABA-induced heat tolerance may involve the adjustment of multiple metabolic processes; how ABA may interact with molecular factors controlling heat tolerance is not well understood
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