Networks of physiological adjustments and defenses, and their synergy with sodium (Na+) homeostasis explain the hidden variation for salinity tolerance across the cultivated Gossypium hirsutum germplasm

Authors: CUSHMAN, KEVIN - Texas Tech University; PABUAYON, ISAIAH - Texas Tech University; Hinze, Lori; SWEENEY, MEGAN - Basf Corporation North America; DE LOS REYES, BENILDO - Texas Tech University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2020
Publication Date: 12/8/2020
Citation: Cushman, K., Pabuayon, I., Hinze, L.L., Sweeney, M., De Los Reyes, B. 2020. Networks of physiological adjustments and defenses, and their synergy with sodium (Na+) homeostasis explain the hidden variation for salinity tolerance across the cultivated Gossypium hirsutum germplasm. Frontiers in Plant Science. 11. Article 588854. https://doi.org/10.3389/fpls.2020.588854.
DOI: https://doi.org/10.3389/fpls.2020.588854

Interpretive Summary: High salt concentration in the soil negatively affects plants by hindering the ability of their roots to absorb water, causing plants to become dehydrated, and, therefore, reducing plant growth and yield. With long term exposure, salt concentration within the plant could accumulate to toxic levels. Relative to most crops, cotton is more tolerant of salt stress; however, there is a perception of limited genetic variability that can be used to improve levels of this stress tolerance. Results of this study showed that increasing the amount of salt compared to levels commonly used in salt studies did reveal noticeable differences in tolerance. The distribution of increased sodium within the plant may contribute to the baseline salt tolerance, but the overall stress tolerance was more often associated with other complex interactions within the plant. This study revealed the baseline tolerance that makes cotton more tolerant to salt than other crop plant species. Understanding the foundations for the baseline tolerance is important because it becomes the basis for interpreting this complex trait. Modern views suggest that stress tolerance involves complex pathways interacting with networks within the plant. These results are the initial step in addressing the long-term goal of revealing variation that could be used for stress tolerance breeding in cotton.

Technical Abstract: After the initial osmotic shock, toxic ions begin to accumulate in tissues of salt stressed plants. In glycophytes, the ability to mobilize or sequester excess ions has been associated with tolerance. Mobilization and sequestration of excess Na+ involves three transport mechanisms namely SOS1 (plasma membrane H+/Na+ antiporter), NHX1 (vacuolar H+/Na+ antiporter), and HKT1 (Na+/K+ transporter in vascular tissue). Plants adapted to sodic soils are assumed to have a better capacity to tolerate cytoplasmic ionic imbalance. Cotton (Gossypium hirsutum L.), a moderately salt tolerant crop plant, has shown variation in response to salinity stress. Differential responses to salt was investigated across a minimal comparative panel representing the spectrum of genetic diversity in the improved cotton germplasm in relation to the spatio-temporal patterns of Na+ accumulation. The goal was to uncover potential physio-morphometric attributes and their interactions that may contribute to overall tolerance potentials in context of the contributions of GhHKT1, GhSOS1, and GhNHX1 to Na+ homeostasis. Multi-dimensional physio-morphometric attributes were investigated in a univariate and multivariate statistical context, as well as, the relationship between variables using structural equation modeling. Results showed that mobilized or sequestered of Na+ may contribute to the baseline salinity tolerance, but the observed variance in overall stress tolerance potential across the comparative panel were more significantly associated to antioxidant capacity, maintenance of stomatal conductance, chlorophyll content, and divalent cations, and other complex physiological interactions.