Response to Long-Term NaHCO3-Derived Alkalinity in Model Lotus japonicus Ecotypes Gifu B-129 and Miyakojima MG-20: Transcriptomic Profiling and Physiological Characterization

Abstract

The current knowledge regarding transcriptomic changes induced by alkalinity on plants is scarce and limited to studies where plants were subjected to the alkaline salt for periods not longer than 48 h, so there is no information available regarding the regulation of genes involved in the generation of a new homeostatic cellular condition after long-term alkaline stress. Lotus japonicus is a model legume broadly used to study many important physiological processes including biotic interactions and biotic and abiotic stresses. In the present study, we characterized phenotipically the response to alkaline stress of the most widely used L. japonicus ecotypes, Gifu B-129 and MG-20, and analyzed global transcriptome of plants subjected to 10 mM NaHCO3 during 21 days, by using the Affymetrix Lotus japonicus GeneChip®. Plant growth assessment, gas exchange parameters, chlorophyll a fluorescence transient (OJIP) analysis and metal accumulation supported the notion that MG-20 plants displayed a higher tolerance level to alkaline stress than Gifu B-129. Overall, 407 and 459 probe sets were regulated in MG-20 and Gifu B-129, respectively. The number of probe sets differentially expressed in roots was higher than that of shoots, regardless the ecotype. Gifu B-129 and MG-20 also differed in their regulation of genes that could play important roles in the generation of a new Fe/Zn homeostatic cellular condition, synthesis of plant compounds involved in stress response, protein-degradation, damage repair and root senescence, as well as in glycolysis, gluconeogenesis and TCA. In addition, there were differences between both ecotypes in the expression patterns of putative transcription factors that could determine distinct arrangements of flavonoid and isoflavonoid compounds. Our results provided a set of selected, differentially expressed genes deserving further investigation and suggested that the L. japonicus ecotypes could constitute a useful model to search for common and distinct tolerance mechanisms to long-term alkaline stress response in plants.

Nutrient deficiency and hypoxia as constraints to Panicum coloratum growth in alkaline soils

“…Nevertheless, since these measurements were performed after plant exposure to alkaline conditions for at least 28 d, it may also be possible that initial responses leading to oxidative stress may have already been mitigated by the induction of antioxidant activity, which, in turn, may have led to a new steady state with low oxidative stress and antioxidant activity. Accordingly, induction of gene expression for antioxidants other than thioredoxins was not mentioned in Lotus plants exposed to alkaline stress for 21 d (Babuin et al ., ), supporting our interpretation. Disclosing the relationship between alkalinity and oxidative stress control would probably require sequenced samplings.…”

“…Most studies on the response of plants to alkaline stress have been performed on plants grown in nutrient solutions (Yang et al ., , ; Li et al ., ; Zhang and Mu, ; Guo et al ., ; Cao et al ., ; Javid et al ., ; Gong et al ., ; Babuin et al ., ; Hu et al ., ) and, exceptionally, in soil (Ahmad et al ., ). However, nutrient solutions do not reproduce all the limitations of alkaline soils; studies performed in hydroponics, with plants supplied with high nutrient concentrations, have only addressed the high pH feature of alkaline soils.…”

Physiological characterization, transcriptomic profiling, and microsatellite marker mining of Lycium ruthenicum

“…Saline-alkaline soil has become a major environmental factor that limits global crop productivity, which adversely hinders the growth and productivity of major crop plants. Alkali soil is characterized by high pH, high exchangeable sodium percentage, and poor fertility; high alkalinity is due to high Na 2 CO 3 and NaHCO 3 content, which exerts a markedly stronger destructive effect on plants than neutral salt soil (Babuin et al, 2014). However, soil salinization and alkalization are often combined in nature; therefore mixed saline-alkaline stresses are the main source of constraint for farming (Shi and Sheng, 2005).…”

Photosynthetic responses mediate the adaptation of two Lotus japonicus ecotypes to low temperature

“…genetic studies due to its relatively small, diploid genome (n = 6), ability to self-fertilize, and short life cycle [2]. The accessibility of mutant databases [3] and complete genome sequencing [4] make this legume a robust tool for plant research, specifically with respect to plant response to biotic and abiotic stress [5,6]. However, few works have addressed the effect of low temperature stress on species of this genus [7].…”