Tissue tolerance mechanisms conferring salinity tolerance in a halophytic perennial species Nitraria sibirica Pall

• Published in: Tree physiology 2021-07, Vol.41 (7), p.1264-1277
• Main Authors: Tang, Xiaoqian, Zhang, Huilong, Shabala, Sergey, Li, Huanyong, Yang, Xiuyan, Zhang, Huaxin
• Format: Article
• Language: English
• ISSN: 1758-4469; 1758-4469
• DOI: 10.1093/treephys/tpaa174

Plant salt tolerance relies on a coordinated functioning of different tissues and organs. Salinity tissue tolerance is one of the key traits that confers plant adaptation to saline environment. This trait implies maintenance low cytosolic Na+/K+ ratio in metabolically active cellular compartments. In this study, we used Nitraria sibirica Pall., a perennial woody halophytes species, to understand the mechanistic basis of its salinity tissue tolerance. The results showed that the growth of seedlings was stimulated by 100-200 mM NaCl treatment. The ions distribution analysis showed that the leaves acted as Na+ sink while plant root possess superior K+ retention. The excessive Na+ absorbed from soil was mainly transported to the shoot and eventually sequestrated into mesophyll vacuoles in the leaves. As a result, N. sibirica could keep optimal balance of K+/Na+ at a tissue- and cell-specific level under saline condition. To enable this, N. sibirica increased both vacuolar H+-ATPase and H+-PPase enzymes activities and up-regulated expressions of NsVHA, NsVP1 and NsNHX1 genes. Vacuolar Na+ sequestration in the leaf mesophyll mediated by NsVHA, NsVP1 and NsNHX1 reduced the Na+ concentration in cytosol and inhibited further K+ loss. Meanwhile, N.sibirica enhanced the TPK expression at the transcriptional level to promote K+ efflux from vacuole into cytoplasm, assisting in maintaining cytosolic K+ homeostasis. It is concluded that the tissue tolerance traits such as vacuolar Na+ sequestration and intracellular K+ homeostasis is critical to confer adaptation of N. sibirica to soil salinity.