Many Hsfs have been characterized in model plants and show considerable functional diversification, being able to play individual roles in complex regulatory networks ( von Koskull-Döring et al., 2007). The function of class-C Hsfs remains unclear studies in rice and wheat suggest that some also show transcriptional activity ( Xue et al., 2014 Hu et al., 2018). Several class-B Hsfs contain a tetrapeptide -LFGV- in the C-terminus, which is assumed to function as a repressor motif by interaction with an unknown co-repressor ( Nover et al., 2001 Scharf et al., 2012). Generally, class-A Hsfs have multiple acidic motifs (AHAs) at the C-terminus and function as transcriptional activators. Based on their structural characteristics, Hsfs are allocated into three major classes, A, B, and C. DBDs recognize and bind to heat-stress elements (HSEs) and ODs are necessary for oligomerization. They all contain a DNA-binding domain (DBD), an oligomerization domain (OD or HR-A/B region), and a nuclear localization signal (NLS) some also contain a nuclear export signal (NES). As sessile organisms, plants cannot escape high temperature instead, they have evolved more complex regulatory mechanisms for Hsfs to avoid damage ( Nover et al., 2001 Kotak et al., 2007).Īlthough higher plants have many Hsfs, they share a conserved modular structure. In eukaryotic organisms, heat-stress transcription factors (Hsfs) are assumed to play a central role in HSR, by inducing the accumulation of heat-shock proteins (Hsps) and by mediating the activation of other heat-responsive genes involved in cell protective mechanisms and the homeostasis of reactive oxygen species (ROS) ( Åkerfelt et al., 2010 Liu et al., 2011 Ohama et al., 2017). To tolerate and survive HS, organisms must activate a heat-stress response (HSR) to alleviate potential damage ( Baniwal et al., 2004). Heat stress transcription factor, heat stress, lily, proline, salt stress, thermotolerance IntroductionĪll organisms sense temperatures above the normal optimum as heat stress (HS), which can disturb cellular homeostasis and cause many adverse growth and developmental effects, and may even lead to death ( Schöffl et al., 1998 Wang et al., 2004 Kotak et al., 2007). Taken together, our results suggested that overexpression of LlHsfA3A or LlHsfA3B caused opposite effects on heat and salt tolerance, which may implicate proline catabolism. Proline catabolism was activated by overexpression, and both LlHsfA3A and LlHsfA3B affected proline oxidation via regulation of AtbZIP11, AtbZIP44, and AtbZIP53 to activate AtproDH1 and AtproDH2 in transgenic Arabidopsis. Under salt stress, proline accumulation was decreased in Arabidopsis and lily with the overexpression of LlHsfA3A or LlHsfA3B. During heat treatments, proline increased in wild-type Arabidopsis plants, but no such increase was detected in transgenic plants that showed better basal or acquired thermotolerance. Further analysis revealed that either LlHsfA3A or LlHsfA3B overexpression altered normal proline accumulation. Using a transient assay, the opposite effects were observed in lily. In both cases, overexpressing plants showed hypersensitivity to salt stress, and a lack of sucrose exacerbated this salt sensitivity. Overexpressing LlHsfA3A in Arabidopsis enhanced its basal and acquired thermotolerance, while overexpressing LlHsfA3B just enhanced its acquired thermotolerance. Both genes were induced by heat stress, but not by salt stress. In this study, we isolated two homologous HsfA3 genes, LlHsfA3A and LlHsfA3B, from lily ( Lilium longiflorum). Although HsfA3 (heat-stress transcription factor A3) is well characterized in heat stress, its roles in other abiotic stresses are less clear.
0 kommentar(er)
