Physiological networks governing salinity tolerance potentials inGossypium hirsutumgermplasm

Abstract

6 7 8 Physiological networks governing salinity tolerance potentials in 9Gossypium hirsutum germplasm 10 One-Sentence Summary: 17Variation in salinity tolerance potential across the tetraploid cultivated 18Gossypium germplasm is better explained by complex physiological networks 19 rather than just cellular Na + homeostasis. 20 1 KRC performed the research, designed the experiment, analyzed the data, co-wrote the manuscript with BGDR; 1 ICMP contributed to the gene expression experiments; 2 LLH assisted in germplasm selection from the GDRS; 3 MES assisted in the design of physiological experiments; 1 BGDR conceptualized the whole project, designed the experiment and wrote the manuscript. ABSTRACT: 21Toxic ions begin to accumulate in tissues of salt-stressed plants after the 22 initial osmotic shock. In glycophytes, the ability to mobilize or sequester excess 23 ions define tolerance mechanisms. Mobilization and sequestration of excess Na + 24 involves three transport mechanisms facilitated by the plasma membrane H + /Na + 25 antiporter (SOS1), vacuolar H + /Na + antiporter (NHX1), and Na + /K + transporter in 26 vascular tissues (HKT1). While the cultivated Gossypium hirsutum (upland 27 cotton) is significantly more tolerant to salinity relative to other crops, the critical 28 factors contributing to the observed variation for tolerance potential across the 29 germplasm has not been fully scrutinized. In this study, the spatio-temporal 30 patterns of Na + accumulation at different severities of salt stress were 31 investigated across a minimal comparative panel representing the spectrum of 32 genetic diversity across the improved cotton germplasm. The goal was to define 33 the importance of integrative or network effects relative to the direct effects of 34 Na + homeostasis mechanisms mediated by GhHKT1, GhSOS1, and GhNHX1. 35 Multi-dimensional physio-morphometric attributes were investigated in univariate 36 and multivariate statistical contexts, as well as the relationship between variables 37 using structural equation modeling. Results showed that mobilized or 38 sequestered Na + may contribute to the baseline salinity tolerance, but the 39 observed variance in overall tolerance potential across a meaningful subset of 40 the germplasm were more significantly associated to antioxidant capacity, 41 maintenance of stomatal conductance, chlorophyll content, and divalent cations, 42and other physiological interactions occurring through complex networks. reduction of long distance Na + transport facilitated by HKT1 and SOS1, and by 67 efficient sequestration of Na + into the root vacuoles through NHX1 and AVP 68 mediated mechanisms (Cheeseman, 1988; Apse et al., 1999; Blumwald et al., 69 2000; Halfter et al., 2000; Maser et al., 2002; Chinnusamy et al., 2004; Haro et 70 al., 2005; Brini et al., 2007). 71Numerous studies in Arabidopsis and several crop plants have shown that 72 positive net gains in salinity tolerance can be achieved with the overexpression of 73 critical genes involved in Na + transport an...

Hidden fractions: Another look at micronutrient and sodium partitioning in modern cotton cultivars

“…Sodium is not essential to cotton and at high levels; it is detrimental to plant health. A substantial body of research has focused on tolerance mechanisms of cotton to excessive levels of Na (Ashraf & Ahmad, 2000; Cushman et al., 2019; Leidi & Saiz, 1997). Excessive Na levels in plant occur due to increasing soil salinity primarily from poor irrigation water quality in semi‐arid regions (Choudhary et al., 2001; Cushman et al., 2019; Niu et al., 2013).…”

“…A substantial body of research has focused on tolerance mechanisms of cotton to excessive levels of Na (Ashraf & Ahmad, 2000; Cushman et al., 2019; Leidi & Saiz, 1997). Excessive Na levels in plant occur due to increasing soil salinity primarily from poor irrigation water quality in semi‐arid regions (Choudhary et al., 2001; Cushman et al., 2019; Niu et al., 2013). High concentrations of Na can cause osmotic stress, ion toxicity, and alterations of the physiological functions of K and Ca in plants (Munns & Tester, 2008; Zhu, 2003).…”