LlWRKY39 is involved in thermotolerance by activating LlMBF1c and interacting with LlCaM3 in lily (Lilium longiflorum)

Abstract

WRKY transcription factors (TFs) are of great importance in plant responses to different abiotic stresses. However, research on their roles in the regulation of thermotolerance remains limited. Here, we investigated the function of LlWRKY39 in the thermotolerance of lily (Lilium longiflorum ‘white heaven’). According to multiple alignment analyses, LlWRKY39 is in the WRKY IId subclass and contains a potential calmodulin (CaM)-binding domain. Further analysis has shown that LlCaM3 interacts with LlWRKY39 by binding to its CaM-binding domain, and this interaction depends on Ca2+. LlWRKY39 was induced by heat stress (HS), and the LlWRKY39-GFP fusion protein was detected in the nucleus. The thermotolerance of lily and Arabidopsis was increased with the ectopic overexpression of LlWRKY39. The expression of heat-related genes AtHSFA1, AtHSFA2, AtMBF1c, AtGolS1, AtDREB2A, AtWRKY39, and AtHSP101 was significantly elevated in transgenic Arabidopsis lines, which might have promoted an increase in thermotolerance. Then, the promoter of LlMBF1c was isolated from lily, and LlWRKY39 was found to bind to the conserved W-box element in its promoter to activate its activity, suggesting that LlWRKY39 is an upstream regulator of LlMBF1c. In addition, a dual-luciferase reporter assay showed that via protein interaction, LlCaM3 negatively affected LlWRKY39 in the transcriptional activation of LlMBF1c, which might be an important feedback regulation pathway to balance the LlWRKY39-mediated heat stress response (HSR). Collectively, these results imply that LlWRKY39 might participate in the HSR as an important regulator through Ca2+-CaM and multiprotein bridging factor pathways.

The CaCIPK3 gene positively regulates drought tolerance in pepper

“…After 48 h of incubation, luciferase activity was detected using a plant-imaging system (Lumazone Pylon 2048B, Princeton, USA) with an 8-min exposure. CaCl 2 and EGTA treatments were performed as described in a previous study 70 .…”

A Novel R2R3-MYB Gene LoMYB33 From Lily Is Specifically Expressed in Anthers and Plays a Role in Pollen Development

“…In transgenic lines, the expression of AtMYB33 and AtMYB65 was also up-regulated, which might stem from their self-activating activity. The expression of AtMYB33, AtMYB65 , and AtCYP704B1 is independent of LoMYB33 expression, and the expression pattern of AtCYP703A2 is opposite that of LoMYB33 (Wu et al, 2019 ; Ding et al, 2021 ). We speculate that this might be explained by a negative feedback regulation mechanism involving LoMYB33 , wherein the high expression of LoMYB33 activates the feedback pathway to control the expression of these genes at a level appropriate for anther development.…”

“…The transcriptional activity was evaluated by growing yeast colonies on SD/-Trp/-His and SD/-Trp/-His with 5 mM 3-AT (3-amino-1,2,4-triazole)-deficient solid media. The transformed yeast cells grown on SD/-Trp medium were also transferred to filter paper for transcriptional activity analysis, and X-α-Gal was added to observe the activity of β-galactosidase (Ding et al, 2021 ).…”

Prediction of temperature tolerance in Lilium based on distribution and climate data

“…While, the heat-resistant (purple) group was consistent with the cold-tolerant group: although the members could adapt to the mean TOF above 25 C, their optimum temperature in the coldest season was roughly the same as the temperate (red) (Tsuchiya et al, 2006;Zieslin and Tsujita, 1988). Among all the groups, only the yellow group corresponded to a value lower than 20 C for the mean TOF, suggesting its potential for extensive application in the areas with low annual cumulative temperatures (Dai et al, 2019;Dorado-Linan et al, 2020). Further phylogenetic analysis and molecular biology research will be useful to explore more interconnections between groups.…”

“…The optimum temperature for Lilium growth is around 18–22°C ( Yin et al., 2007 ; Xin et al., 2010 ). High temperature (>28°C) has negative effects on the growth of Lilium such as short stems, reduced number of flower buds, shortened flower bud length ( Steininger and Pasian, 2003 ; Ding et al., 2021 ). Besides, previous studies showed that cold stress inhibit the growth of lily bulbs: for non-hardy taxa, –6°C can lead to bulb lethality in most cases; at –8°C, virtually all bulbs were dead and did not regrow ( Du and Anderson, 2009 ; Tian et al., 2020 ).…”