Plant growth-promoting rhizobacteria (PGPR) is a beneficial group of free-living soil bacteria that colonize the rhizosphere and are helpful in root growth and development. PGPR plays an important role in plant growth through the production of phytohormones, solubilization of inorganic phosphate, increased iron nutrition via iron-chelating siderophores and volatile compounds that affect the plant metabolism and signalling pathways. Additionally, PGPR shows synergistic and antagonistic interactions with rhizosphere microorganisms and soil which indirectly improve and enhance plant growth rate. Various environmental factors affect the PGPR growth and proliferation in the plants. There are several shortcomings and limitation in the PGPR research which can be addressed through the use of modern approaches and techniques by exploring multidisciplinary research which combines applications in microbiology, biotechnology, nanotechnology, agro-biotechnology, and chemical engineering. Furthermore, PGPR is also known to reduce the emission of greenhouse gases (GHGs), carbon footprint, and also increase the nutrient-use efficiency. Here we describe the importance of PGPR in sustainable agriculture and their role in plant growth and development.

Cadmium (Cd) is one of the toxic heavy metals not essential for the growth and development of plants and other organisms. Brassica rapa accumulates several heavy metals in its leaves and is reportedly suitable for phytoremediation. In this study, Cd uptake and accumulation in the leaves of B. rapa exposed to different cadmium levels (0, 5, 10, 20, 50, 100 μM CdSO4) were analyzed, as well as the effect of Cd stress on HMA2 and HMA4 genes expression were investigated. The qRT-PCR results showed that HMA2 and HMA4 play a vital role in cadmium uptake and translocation in B. rapa at low Cd levels (5-20 μM). However, exposure to high Cd levels (50 and 100 μM) significantly reduced the growth and biomass of B. rapa. Furthermore, high levels of Cd inhibit the expression of HMA2 and HMA4 genes in B. rapa. Our data show a multigenetic (co-acting of many transporter gene clusters) response in the signaling pathway associated with Cd accumulation and tolerance mechanism in B. rapa.

Arabidopsis thaliana has eight genes encoding members of the type P1B heavy metal–transporting ATPase, subfamily of the P-type ATPases. We focused our study on four ATPases, mainly HMA1, HMA2, HMA3, and HMA4, which are closely related and most similar in their sequences. We carried out the bioinformatics analysis of these metal ATPases and obtained their structure in A. thaliana, A. halleri, and the other heavy metal accumulators in Brassica spp. A. thaliana is a model plant for research because of the duplications and other evolutionary events. These evolutionary events provided a chance to elucidate their regulation and function in the cell. All previous bioinformatics analyses have given some information about their structure, but not much work has been done on their structural components and interactome analysis. Experimental determination of 3D structures is essential to understand better these proteins’ function, which is crucial for the proper functioning of all plant cellular processes. Especially, docking sites and domains need to be worked out to understand the role of these transporter proteins and their interaction in plant cells. These bioinformatic analyses will help the researcher understand these ATPases’ role in detoxifying the toxic metals from the cells of accumulator plants. Further research on gene cloning, gene expression, and generating new accumulator plants for phytoremediation is needed to reclamation polluted soils from toxic heavy metals.

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