Search

Key Message: OscWRKY1 from Ocimum sanctum positively regulates phenylpropanoid pathway genes and rosmarinic acid content. OscWRKY1 overexpression promotes resistance against bacterial pathogen in Arabidopsis. WRKY transcription factor (TF) family regulates various developmental and physiological functions in plants. PAL genes encode enzymes which are involved in plant defense responses, but the direct regulation of PAL genes and phenylpropanoid pathway through WRKY TF's is not well characterized. In the present study, we have characterized an OscWRKY1 gene from Ocimum sanctum which shows induced expression by methyl jasmonate (MeJA), salicylic acid (SA), and wounding. The recombinant OscWRKY1 protein binds to the DIG-labeled (Digoxigenin) W-box cis-element TTGAC[C/T] and activates the LacZ reporter gene in yeast. Overexpression of OscWRKY1 enhances Arabidopsis resistance towards Pseudomonas syringae pv. tomato Pst DC3000. Upstream activator sequences of PAL and C4H have been identified to contain the conserved W-box cis-element (TTGACC) in both O. sanctum and Arabidopsis. OscWRKY1 was found to interact with W-box cis-element present in the PAL and C4H promoters. Silencing of OscWRKY1 using VIGS resulted in reduced expression of PAL, C4H, COMT, F5H and 4CL transcripts. OscWRKY1 silenced plants exhibit reduced PAL activity, whereas, the overexpression lines of OscWRKY1 in Arabidopsis exhibit increased PAL activity. Furthermore, the metabolite analysis of OscWRKY1 silenced plants showed reduced rosmarinic acid content. These results revealed that OscWRKY1 positively regulates the phenylpropanoid pathway genes leading to the alteration of rosmarinic acid content and enhances the resistance against bacterial pathogen in Arabidopsis., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

As waterlogging and successive events severely influence growth and development of economically important plants, we attempted to characterize the role of a waterlogging-responsive group I (A-6) ethylene response factor (MaRAP2-4) from Mentha arvensis. Waterlogging, ethylene and methyl jasmonate rapidly induced the expression of MaRAP2-4. MaRAP2-4 interacted with multiple cis-elements like dehydration response elements (DRE1/2), anoxia/jasmonic acid response element (JARE) and GCC box showing its involvement in multiple responses. MaRAP2-4 localizes in the nucleus and acts as a transcriptional activator. Truncation and internal deletion identified a 20 amino acids potential transactivation domain (PLPSSVDAKLEAICQSLAIN) in MaRAP2-4. MaRAP2-4 transgenic Arabidopsis showed enhanced waterlogging and subsequent oxidative stress tolerance. Microarray analysis revealed that within up-regulated genes 483, 212 and 132 promoters carry either single or multiple copies of DRE, JARE and GCC cis-element/s, respectively. Within these promoters, a large section belongs to carbohydrate metabolism/transport, including many SWEET transporters. Further analysis showed MaRAP2-4 specifically targets two positions in AtSWEEET10 promoter carrying DRE and/or GCC box that might regulate carbohydrate availability and waterlogging tolerance. These results demonstrate that MaRAP2-4 is a positive regulator of waterlogging tolerance, and as energy-consuming processes such as carbohydrate biosynthesis are reduced under waterlogging-induced hypoxia, sugar transport through SWEETs may be the primary option to make sugar available to the required tissue., (© 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

Plants posses a complex co-regulatory network which helps them to elicit a response under diverse adverse conditions. We used an in silico approach to identify the genes with both DRE and ABRE motifs in their promoter regions in Arabidopsis thaliana. Our results showed that Arabidopsis contains a set of 2,052 genes with ABRE and DRE motifs in their promoter regions. Approximately 72% or more of the total predicted 2,052 genes had a gap distance of less than 400 bp between DRE and ABRE motifs. For positional orientation of the DRE and ABRE motifs, we found that the DR form (one in direct and the other one in reverse orientation) was more prevalent than other forms. These predicted 2,052 genes include 155 transcription factors. Using microarray data from The Arabidopsis Information Resource (TAIR) database, we present 44 transcription factors out of 155 which are upregulated by more than twofold in response to osmotic stress and ABA treatment. Fifty-one transcripts from the one predicted above were validated using semiquantitative expression analysis to support the microarray data in TAIR. Taken together, we report a set of genes containing both DRE and ABRE motifs in their promoter regions in A. thaliana, which can be useful to understand the role of ABA under osmotic stress condition., (© 2013 Institute of Botany, Chinese Academy of Sciences.)

Summary: As waterlogging and successive events severely influence growth and development of economically important plants, we attempted to characterize the role of a waterlogging‐responsive group I (A‐6) ethylene response factor (MaRAP2‐4) from Mentha arvensis. Waterlogging, ethylene and methyl jasmonate rapidly induced the expression of MaRAP2‐4. MaRAP2‐4 interacted with multiple cis‐elements like dehydration response elements (DRE1/2), anoxia/jasmonic acid response element (JARE) and GCC box showing its involvement in multiple responses. MaRAP2‐4 localizes in the nucleus and acts as a transcriptional activator. Truncation and internal deletion identified a 20 amino acids potential transactivation domain (PLPSSVDAKLEAICQSLAIN) in MaRAP2‐4. MaRAP2‐4 transgenic Arabidopsis showed enhanced waterlogging and subsequent oxidative stress tolerance. Microarray analysis revealed that within up‐regulated genes 483, 212 and 132 promoters carry either single or multiple copies of DRE, JARE and GCC cis‐element/s, respectively. Within these promoters, a large section belongs to carbohydrate metabolism/transport, including many SWEET transporters. Further analysis showed MaRAP2‐4 specifically targets two positions in AtSWEEET10 promoter carrying DRE and/or GCC box that might regulate carbohydrate availability and waterlogging tolerance. These results demonstrate that MaRAP2‐4 is a positive regulator of waterlogging tolerance, and as energy‐consuming processes such as carbohydrate biosynthesis are reduced under waterlogging‐induced hypoxia, sugar transport through SWEETs may be the primary option to make sugar available to the required tissue. [ABSTRACT FROM AUTHOR]