Research

Every stage of a plant’s life is influenced by the light conditions which it grows in. In addition to their obligate dependence on light for photosynthesis, plants perceive light as an environmental signal to adjust their growth pattern during seedling development, to mediate the synthesis of pigment molecules, to detect the competition from their neighborhood, and to monitor the change of seasons. Plants have evolved highly sophisticated molecular machinery that can perceive the light signals from their environment and channel this information to their gene expression network. We study the components of this signaling pathway and their mechanisms of action at the molecular level for a deeper understanding of the light-regulated developmental responses in plants. Our work is mainly focused on the role of a family of zinc-finger transcription factors called B-box (BBX) proteins. We investigate the role of these proteins and their association with major other light signaling factors in early seedling development and regulation of flowering time (Job et al., 2018; Vaishak et al., 2019). We also study how the light signaling components interplay with the phytohormone network inside the plant to optimize seedling development. We have recently identified the key role of CONSTITUTIVELY PHOTOMORPHGENIC1 (COP1) and ELONGATED HYPOCOTYL5 (HY5), two central regulators of light signaling, in determining the action of phytohormone abscisic acid (ABA) during early seedling development (Yadukrishnan et al., 2020a,b). We are also trying to identify the role of several BBX proteins in integrating light and hormonal signaling pathways at various stages of plant development.

• Job N, Yadukrishnan P, Bursch K, Datta, S, Johansson H (2018). Two B-box proteins regulate photomorphogenesis by oppositely modulating HY5 through their diverse C-terminal domains. Plant Physiology. DOI: 10.1104/pp.17.00856
• Vaishak KP, Yadukrishnan P, Bakshi S, Kushwaha AK, Ramachandran H, Job N, Babu D, Datta, S (2019) The B-box Bridge between Light and Hormones in Plants. Journal of Photobiology and Photochemistry:B. DOI: 10.1016/j/jphotobiol.2018.12.021
• Yadukrishnan P, Rahul PV, Datta S (2020b) HY5 suppresses, rather than promotes, ABA-mediated inhibition of post-germination seedling development. Plant Physiology. DOI: 10.1104/pp.20.00783
• Yadukrishnan P, Rahul PV, Ravindran N, Bursch K, Johansson H, Datta S (2020a) CONSTITUTIVELY PHOTOMORPHOGENIC1 promotes ABA-mediated inhibition of post-germination seedling establishment. The Plant Journal. DOI: 10.1111/tpj.14844.

Solar UV radiation has substantial effects on the growth and fitness of terrestrial organisms. UV radiation, based on its wavelength can be subdivided into UV-A (315-400nm), UV-B (280-315nm) and UV-C (200-280nm). UV-B can harm plant growth depending on its dosage and the duration of exposure (Jenkins, 2017). When exposed to longer wavelength and lower doses of UV-B, plants adjust their growth by undergoing morphogenic changes, whereas shorter wavelength and higher doses of UV-B induce stress responses. Study of UV-B signaling and identification and characterization of regulators of UV-B tolerance in plants can allow us to generate plants with enhanced ability to cope UV-B stress. UV-B signals are perceived by a dedicated photoreceptor named UVR8. Several intermediate proteins such as COP1, RUP1, RUP2, WRKY36 act downstream to UVR8 and play key roles in the UV-B signaling. HY5 acts further downstream to these proteins and activates genes to induce physiological and developmental changes in response to UV-B. Precise spatiotemporal control over the function of HY5 is ensured by several cofactor proteins. B-box (BBX) proteins constitute a family of zinc-finger transcription factors that are known to regulate wide range of light-mediated developmental processes, often in association with HY5. Even though the role of BBX proteins in white light signaling is well established, their role in UV-B signaling is poorly understood. Recently, we identified that a B-box protein, BBX31, promotes tolerance against UV-B stress in Arabidopsis. BBX31 overexpressing lines displayed enhanced tolerance towards high dose of UV-B by promoting the accumulation of protective compounds, altering the levels of primary metabolites, and modifying the expression of DNA-repair genes (Yadav et al., 2019a, b). Our study indicates an unexplored possibility that several among the BBX family members play important roles in UV-B signaling and response. We are trying to identify and characterize the unknown roles of BBX proteins in regulating the UV-B signaling pathway.

• Yadav A, Bakshi S, Yadukrishnan P, Lingwan M, Dolde U, Wenkel S, Masakapalli SK, Datta, S (2019) The B-box containing microprotein miP1a/BBX31 regulates photomorphogenesis and UV-B protection in Arabidopsis. Plant Physiology. DOI: https://doi.org/10.1104/pp.18.01258.

Phosphorous is a component of fundamental biomolecules like ATP, DNA, phospholipids etc. Thus, phosphate levels and soil pH are key factors that regulate plant health and crop production. Phosphate is highly reactive and forms insoluble complexes with cations like Al³⁺, Fe³⁺ and Ca²⁺ on the surface of soil particles rendering it unavailable to the plants. In acidic soils (soils with pH<5), plant growth is inhibited mainly due to the presence of Al³⁺ that reduces phosphate availability and is toxic to root growth. To increase the yield, farmers add phosphate-rich fertilizers to the soil. Dependence on phosphate fertilizers is not a sustainable solution, as they are nonrenewable mined resources and are hazardous to the environment when used in excess. A more sustainable strategy is to enhance the ability of plants to grow well under low phosphate and aluminium stresses. Plants that inherently show enhanced tolerance to these stresses can provide clues to engineer tolerance in susceptible species and varieties. The exudation of organic acids from root is a common natural mechanism to tolerate both low phosphate and aluminium stress. Citrate ions are highly effective in binding and sequestering Al³⁺. The exudation of the citrate involves a membrane transporter belonging to the MATE (Multidrug and Toxic Extrusion) family. We are interested in identifying and characterizing MATE genes and use these genes to generate plants that can tolerate both low phosphate and aluminium stress in Arabidopsis and Soybean. We have collated the roles of all known MATE transporters in plants together with their structural details (Upadhyay et al., 2019). Recently, we have identified that the MATE transporter DTX30 modulates auxin levels in the root to regulate root development and promotes citrate exudation to alleviate aluminium toxicity (Upadhyay et al.,2020). In future, we intend to test the role of some of these MATE transporters in Soybean and other crop plants, and to make these crops less dependent on phosphate fertilizers. In addition to these specific themes, we study the mechanisms by which plants integrate the external light signals with their internal hormonal signaling pathways to modify their growth and development. We also explore the effects of quantity and quality of light on the ability of plants in acquiring different nutrients from the soil.

• Upadhyay N, Kar D, Datta S (2020) A Multidrug and Toxic compound Extrusion (MATE) transporter modulates auxin levels in root to regulate root development and promotes aluminium tolerance. Plant, Cell & Environment. DOI: 10.1111/pce.13658.
• Upadhyay N, Kar D, Mahajan Deepak B, Nanda S, Rahiman R, Panchakshari N A, Bhagavatula L, Datta S (2019) The multitasking abilities of MATE transporters in plants. Journal Of Experimental Botany. DOI: https://doi.org/10.1093/jxb/erz246