Creation of Transgenic Cotton Overexpressing Salt Tolerant PP2A-C5 and Salt/Drought Tolerant AVP1

The United States is the third largest cotton producer in the world and Texas is the No. 1 cotton producer in the US responsible for ~30% of nation’s cotton production. In Texas High Plains, drought and saline soils are the major limiting factors that reduce quantity and quality of cotton fibers. Also, the excessive use of fertilizers results in salt accumulation in cotton lands. This is in part due to severe drought conditions in dryland agricultural systems. In some instances, lands are no longer suitable for cotton production. This research uses Agrobacterium-mediated plant transformation to co-overexpress PP2A-C5 and AVP1 in cotton in order to generate a cotton variety that can outperform conventional cotton varieties under dryland and irrigated agricultural systems. PP2A-C5 is the catalytic subunit 5 of Arabidopsisprotein phosphatase 2A. Arabidopsis thaliana plants overexpressing PP2A-C5 are more tolerant to high concentrations of NaCl, KCl, and KNO3. PP2A-C5 mediated multi-salt tolerance is possibly achieved via positive up-regulation of the chloride channel proteins localized on the vacuolar membrane, e.g. CLCa and CLCc, which import NO3- and Cl- ions into vacuoles, respectively, at the expense of protons. AVP1, a vacuolar membrane bound H+ pyrophosphatase acidifies the vacuole. Therefore, the overexpression of AVP1 provides ample H+ availability in the vacuole to energize chloride ion channels, further enhancing NO3- , K+, and Cl- uptake. It also activates other secondary transporters such as Na+/H+ antiporters, K+, NO3-, and inorganic PO43- transporters. As a result, the osmotic pressure of the vacuole is increased making the transgenic plants more drought- and salt-tolerant. Also, these plants will be more efficient in nitrate, phosphate, and potassium (NPK) absorption. Therefore, these transgenic plants will be expected to outperform AVP1-overexpressing and PP2A-C5-overexpressing cotton plants in terms of drought and salinity tolerance and fertilizer use efficiency.