SbMYB15 transcription factor mitigates cadmium and nickel stress in transgenic tobacco by limiting uptake and modulating antioxidative defence system

Abstract

Plants require different inorganic minerals in an appropriate amount for growth; however, imbalance can limit growth and productivity. Heavy metal accumulation causes toxicity and generates signalling crosstalk with reactive oxygen species (ROS), phytohormones, genes and transcription factors (TFs). The MYB (myeloblastoma) TFs participate in plant processes such as metabolism, development, cell fate, hormone pathways and responses to stresses. This is the first report towards characterisation of R2R3-type MYB TF, SbMYB15, from succulent halophyte Salicornia brachiata Roxb. for heavy metal tolerance. The SbMYB15 showed >5-fold increased transcript expression in the presence of CdCl2 and NiCl2•6H2O. The constitutive overexpression of SbMYB15 conferred cadmium and nickel tolerance in transgenic tobacco, with improved growth and chlorophyll content. Further, the transgenics showed reduced generation of reactive oxygen species (H2O2 and O2•−) as compared with the wild-type (WT) with both Cd2+ and Ni2+ stress. Transgenics also showed low uptake of heavy metal ions, increased scavenging activity of the antioxidative enzymes (CAT and SOD) and higher transcript expression of antioxidative genes (CAT1 and MnSOD). Thus, the present study signifies that SbMYB15 can be deployed for developing heavy metal tolerance in crop plants via genetic engineering.

Reactive Oxygen Species and Antioxidant Defense in Plants under Abiotic Stress: Revisiting the Crucial Role of a Universal Defense Regulator

“…Superoxide dismutase and APX genes may serve as a positive regulator to increased salt tolerance by the regulation of ROS and lignin biosynthesis signaling pathways in transgenic plants [ 265 ]. Transgenic tobacco exhibited tolerance to heavy metals and overexpression of SbMYB15 enhanced the activities of CAT and SOD, also increasing the expression of MnSOD at 100 μM (2-fold) and 300 μM (3-fold) of CdCl 2 , as well as CAT1 by 62- and 9-fold at 100 and 300 μM of CdCl 2 [ 266 ]. In regard to heavy metal tolerance, CaGrx from chickpea was overexpressed in A. thaliana .…”

Genome-wide identification of myeloblastosis gene family and its response to cadmium stress in Ipomoea aquatica

“…Transcription factors (TFs) act as crucial regulators for plant Cd accumulation and tolerance, which execute their functions by switching “on” or “off” downstream gene expression. Several TFs that involved in plant response to Cd stress have been reported, including basic helix–loop–helix protein (bHLH) ( Xu et al, 2017 ), dehydration-responsive element-binding protein (DREB) ( Akbudak et al, 2018 ), metal-responsive element-binding transcription factor (MTF) ( Sun et al, 2015 ), ethylene-responsive factor (ERF) ( Tian et al, 2022 ) basic leucine Zipper (bZIP) ( Lu et al, 2022 ), WRKY ( Sheng et al, 2019 ), and MYB ( Sapara et al, 2019 ).…”

Molecular-Assisted Breeding of Cadmium Pollution-Safe Cultivars

“…Vacuole sequestration plays important roles in the transport and detoxification of Cd in yeasts and plants. − Cd-complexes is sequestered into the vacuoles by membrane transporters such as OsHMA3 (heavy metal ATPase 3) and OsABCC9 (C-type ABC transporter 9). − OsHMA3 encodes a tonoplast-localized P1B-type heavy metal ATPase responsible for transporting Cd and Zn, in which several alleles of OsHMA3 associated with different Cd accumulation in rice grain. Several alleles with weak or no Cd transport activity can restrict Cd transport to vacuoles, promote root to-shoot Cd translocation, and lead to high Cd accumulation in rice grain. ,,− , TdHMA3B1a, with functional allele in a low grain Cd cultivar of durum wheat, is able to transport more Cd into the vacuole and reduce Cd accumulation in grain when compared to the cultivar with nonfunctional allele in TdHMA3B1 . Hypofunctional AtHMA3 identified by genome-wide association studies and biparental linkage mapping is able to promote Cd accumulation in the leaves compared to those with functional AtHMA3 in A .…”

“…Furthermore, Cd-responsive transcription factors (TFs) contributed to the development of Cd-PSCs through transgenic methods. Transgenic tobacco overexpressing TF SbMYB15 from succulent halophyte Salicornia brachiata Roxb displayed high Cd/Ni tolerance with low Cd/Ni uptake traits by increasing the activity of antioxidative enzymes (CAT and SOD) and the expression of antioxidative genes (CAT1 and MnSOD) . Overexpression of AemNAC2 in the wheat cultivar “Bobwhite” suppresses NRAMP5 and HMA2 , enhancing Cd tolerance by reducing Cd concentration in the roots, shoots, and grains .…”