Co‐expression of tonoplast Cation/H+ antiporter and H+‐pyrophosphatase from xerophyte Zygophyllum xanthoxylum improves alfalfa plant growth under salinity, drought and field conditions

• Published in: Plant biotechnology journal Vol. 14; no. 3; pp. 964 - 975
• Main Authors: Bao, Ai‐Ke, Du, Bao‐Qiang, Touil, Leila, Kang, Peng, Wang, Qiang‐Long, Wang, Suo‐Min
• Format: Journal Article
• Language: English
• Published: England Blackwell Pub 01-03-2016; John Wiley & Sons, Inc
• Subjects: abiotic stress; Accumulation; Adaptation, Physiological - drug effects; Adaptation, Physiological - genetics; Agrobacterium; Alfalfa; antiporters; Aridity; Calcium; Calcium - metabolism; Calcium ions; Cations; Conductance; co‐expression; Crop yields; Drought; Droughts; Environmental factors; Flowers & plants; forage legumes; forage yield; Gene expression; Gene Expression Regulation, Plant - drug effects; Genes; greenhouses; growth performance; H+‐PPase; Hydrogen; Inorganic Pyrophosphatase - metabolism; ions; leaves; Legumes; Medicago sativa - growth & development; Medicago sativa - physiology; Moisture content; Osmoregulation; Photosynthesis; Photosynthesis - drug effects; Physiological aspects; Plant growth; Plant Leaves - metabolism; Plants, Genetically Modified; potassium; Potassium - metabolism; Productivity; Pyrophosphatase; Resistance; roots; Salinity; Salinity effects; Salt; sodium; Sodium - metabolism; Sodium chloride; Sodium Chloride - pharmacology; Sodium-Hydrogen Exchangers - metabolism; Stomata; Stomatal conductance; stress tolerance; Studies; tonoplast; tonoplast NHXs; transgenic alfalfa; Transgenic plants; Vacuoles - metabolism; Variance analysis; Water - metabolism; Water content; water use efficiency; xerophytes; Zygophyllum; Zygophyllum - drug effects; Zygophyllum - metabolism; Zygophyllum xanthoxylum; China; co-expression; stress tolerance; transgenic alfalfa; tonoplast NHXs; H+-PPase
• ISSN: 1467-7644; 1467-7652
• DOI: 10.1111/pbi.12451

Salinity and drought are major environmental factors limiting the growth and productivity of alfalfa worldwide as this economically important legume forage is sensitive to these kinds of abiotic stress. In this study, transgenic alfalfa lines expressing both tonoplast NXH and H⁺‐PPase genes, ZxNHX and ZxVP1‐1 from the xerophyte Zygophyllum xanthoxylum L., were produced via Agrobacterium tumefaciens‐mediated transformation. Compared with wild‐type (WT) plants, transgenic alfalfa plants co‐expressing ZxNHX and ZxVP1‐1 grew better with greater plant height and dry mass under normal or stress conditions (NaCl or water‐deficit) in the greenhouse. The growth performance of transgenic alfalfa plants was associated with more Na⁺, K⁺ and Ca²⁺ accumulation in leaves and roots, as a result of co‐expression of ZxNHX and ZxVP1‐1. Cation accumulation contributed to maintaining intracellular ions homoeostasis and osmoregulation of plants and thus conferred higher leaf relative water content and greater photosynthesis capacity in transgenic plants compared to WT when subjected to NaCl or water‐deficit stress. Furthermore, the transgenic alfalfa co‐expressing ZxNHX and ZxVP1‐1 also grew faster than WT plants under field conditions, and most importantly, exhibited enhanced photosynthesis capacity by maintaining higher net photosynthetic rate, stomatal conductance, and water‐use efficiency than WT plants. Our results indicate that co‐expression of tonoplast NHX and H⁺‐PPase genes from a xerophyte significantly improved the growth of alfalfa, and enhanced its tolerance to high salinity and drought. This study laid a solid basis for reclaiming and restoring saline and arid marginal lands as well as improving forage yield in northern China.