Abstract
Rhythms produced by the endogenous circadian clock play a critical role in allowing plants to respond and adapt to the environment. While there is a well-established regulatory link between the circadian clock and responses to abiotic stress in model plants, little is known of the circadian system in crop species like soybean. This study examines how drought impacts diurnal oscillation of both drought responsive and circadian clock genes in soybean. Drought stress induced marked changes in gene expression of several circadian clock-like components, such as LCL1-, GmELF4- and PRR-like genes, which had reduced expression in stressed plants. The same conditions produced a phase advance of expression for the GmTOC1-like, GmLUX-like and GmPRR7-like genes. Similarly, the rhythmic expression pattern of the soybean drought-responsive genes DREB-, bZIP-, GOLS-, RAB18- and Remorin-like changed significantly after plant exposure to drought. In silico analysis of promoter regions of these genes revealed the presence of cis-elements associated both with stress and circadian clock regulation. Furthermore, some soybean genes with upstream ABRE elements were responsive to abscisic acid treatment. Our results indicate that some connection between the drought response and the circadian clock may exist in soybean since (i) drought stress affects gene expression of circadian clock components and (ii) several stress responsive genes display diurnal oscillation in soybeans.
Highlights
Plants are subjected to diurnal oscillations due the planet movement around its axis, which generates light and temperature variations
We evaluated the expression of a GmbZIP1 transcription factor that belongs to the AREB subfamily and is reported to be an abiotic stress- and abscisic acid (ABA)-responsive gene [72]
Our results show that the drought stress affects the gene expression of circadian clock components in soybeans
Summary
Plants are subjected to diurnal oscillations due the planet movement around its axis, which generates light and temperature variations. The ABAindependent pathway involves ethylene signaling and the participation of transcription factors, primarily from the ethyleneresponsive factor (ERF) and C-repeat-binding factor/dehydrationresponsive element-binding (CBF/DREB) subfamilies [1,5]. In both the ABA-dependent and ABA-independent pathways, transcription factors bind to specific cis-elements and induce several stress-responsive genes that encode different protein classes, including galactinol synthase (a key enzyme for the biosynthesis of the osmoprotectant molecule raffinose) [6], RAB18 (a protein involved in membrane vesicle transport) [7], Remorins (membrane structural proteins) [8], and peroxidases (ROSscavenging proteins) [9]
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