Thiamin-induced variations in oxidative defense processes in white clover ( Trifolium repens L.) under water deficit stress

Abstract

Introduction World food security is being significantly hampered due to water scarcity (Mitter et al., 2015). Water stress is different from other stresses because unlike other natural disasters its effects remain even after its period terminates (Ashraf et al., 2010; Strauss et al., 2013). Soil water deficiency affects three major mechanisms in plants: reduced canopy absorption of photosynthetically available radiation (PAR), radiation use efficiency, and harvest index, and all of these lead to reduced plant yield (Fiala et al., 2014). Seedling growth and productivity are also severely affected, mainly due to low supply of water (Atkinson and Urwin, 2012). Due to drought stress, germination potential (Wang et al., 2011), hypocotyl length, and plant biomass are commonly hampered (Wang et al., 2015). During the initial stage of growth and germination, relative water content was high in wheat, which decreased as dry matter accumulated and leaf matured (Hajheidari et al., 2007; Kaur et al., 2007). Nutrient uptake and tissue level concentrations along with water relations are perturbed under water-limited conditions in crop plants (Losak et al., 2010). Drought stress causes the production of reactive oxygen species (ROS), which affect the ultrastructure of cell membranes and DNA as well as the functioning of cellular processes (Turkan, 2011; Sun et al., 2013; Kaya et al., 2015). ROS including hydroxyl radical, anion radical, hydrogen peroxide, alkyl radicals, and singlet oxygen are injurious to plant metabolic activities. These species may react to lipids, proteins, and DNA, which causes oxidative damage and abnormal functions of cells (Sarvajeet and Tuteja, 2010; Shafiq et al., 2015). It is known that absorption of thiamin by plant root, leaves, and

Thiamin stimulates growth and secondary metabolites in turnip (Brassica rapa L.) leaf and root under drought stress

“…However, exogenous application of thiamin was effective in lowering the oxidative stress both in leaves and roots by enhancing the antioxidants content (AsA and total phenolics) and the activities of antioxidant enzymes (SOD, POD and CAT) in both turnip cultivars under drought stress conditions. It is somewhat similar to what has earlier been observed by Ghafar et al (2019) in white clover, where ascorbic acid concentration increased in both white clover cultivars under water deficit conditions. However, in contradiction to the present study, thiamin spray did not improve these contents in the white clover plants.…”

“…In addition, exogenous application of thiamin improved the chlorophyll pigments in both turnip cultivars under stress and non‐stress conditions. Likewise, in another study, foliar‐applied thiamin enhanced the chlorophyll content at 100 mM in two cultivars of white clover under water‐deficit conditions (Ghafar et al 2019). An earlier study by Alipoor and Mohsenzadeh (2012) showed that thiamin improved chlorophyll pigments in Aloe vera under nickel stress and in sunflower under saline conditions (Sayed and Gadallah 2002).…”

“…So, stress‐induced deficiency in the accumulation of vitamins is one of the primary symptoms for metabolic knock‐on under water deficiency (Hanson et al 2016, Sanjari et al 2019). In a previous study with white clover ( Trifolium repens L.), Ghafar et al (2019) reported that foliage spray of 50 mM thiamin improved plant growth under drought stress conditions. They attributed this growth improvement to thiamin‐induced increase in the photosynthetic pigments and total phenolics of white clover plants under water deficit conditions.…”

“…After 30 days of water‐deficit conditions, three levels [0 mM (control, distilled water), 50 and 100 mM)] of thiamin (MP Biomedical Inc.) prepared in distilled water along with Tween‐20 (0.1%) were applied to all turnip plants (except the controls) as a foliar spray using a plastic hand pump. A total of 25 ml thiamine solution (of each thiamin level) were applied per pot and per treatment (Ghafar et al 2019).…”

Metabolic engineering provides insight into the regulation of thiamin biosynthesis in plants

“…Recently, attention has been drawn toward metabolic engineering of plant thiamin content as a means to enhance nutritional value while improving stress resilience ( Dong et al., 2015 , 2016 ; Goyer, 2017 ; Strobbe and Van Der Straeten, 2018 ; Fitzpatrick and Chapman, 2020 ). The reasoning behind this is that enhancement of in planta thiamin levels, whether achieved by exogenous application or by metabolic engineering, increases tolerance to biotic ( Bahuguna et al, 2012 ; Dong et al., 2015 ; Vinchesi et al., 2017 ; Hamada et al., 2018 ) and abiotic stresses, such as salt/oxidative stress ( Yee et al, 2016 ; Kaya et al., 2018 ; El-Shazoly et al., 2019 ) and drought ( Li et al., 2016 ; Ghafar et al., 2019 ). The increase of plant thiamin levels is, therefore, highly encouraged, as it would ameliorate global health as well as aid in ensuring sufficient crop yield by tackling stress tolerance.…”