AUTHOR=Reddy Palakolanu Sudhakar , Dhaware Mahamaya G. , Sivasakthi Kaliamoorthy , Divya Kummari , Nagaraju Marka , Sri Cindhuri Katamreddy , Kavi Kishor Polavarapu Bilhan , Bhatnagar-Mathur Pooja , Vadez Vincent , Sharma Kiran K. 

TITLE=Pearl Millet Aquaporin Gene PgPIP2;6 Improves Abiotic Stress Tolerance in Transgenic Tobacco

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.820996

DOI=10.3389/fpls.2022.820996

ISSN=1664-462X

ABSTRACT=<p>Pearl millet [<italic>Pennisetum glaucum</italic> (L) R. Br.] is an important cereal crop of the semiarid tropics, which can withstand prolonged drought and heat stress. Considering an active involvement of the <italic>aquaporin</italic> (AQP) genes in water transport and desiccation tolerance besides several basic functions, their potential role in abiotic stress tolerance was systematically characterized and functionally validated. A total of 34 <italic>AQP</italic> genes from <italic>P. glaucum</italic> were identified and categorized into four subfamilies, viz., plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin-26-like intrinsic proteins (NIPs), and small basic intrinsic proteins (SIPs). Sequence analysis revealed that <italic>PgAQPs</italic> have conserved characters of <italic>AQP</italic> genes with a closer relationship to sorghum. The <italic>PgAQPs</italic> were expressed differentially under high vapor pressure deficit (VPD) and progressive drought stresses where the <italic>PgPIP2;6</italic> gene showed significant expression under high VPD and drought stress. Transgenic tobacco plants were developed by heterologous expression of the <italic>PgPIP2;6</italic> gene and functionally characterized under different abiotic stresses to further unravel their role. Transgenic tobacco plants in the T<sub>2</sub> generations displayed restricted transpiration and low root exudation rates in low- and high-VPD conditions. Under progressive drought stress, wild-type (WT) plants showed a quick or faster decline of soil moisture than transgenics. While under heat stress, <italic>PgPIP2;6</italic> transgenics showed better adaptation to heat (40°C) with high canopy temperature depression (CTD) and low transpiration; under low-temperature stress, they displayed lower transpiration than their non-transgenic counterparts. Cumulatively, lower transpiration rate (Tr), low root exudation rate, declined transpiration, elevated CTD, and lower transpiration indicate that <italic>PgPIP2;6</italic> plays a role under abiotic stress tolerance. Since the <italic>PgPIP2;6</italic> transgenic plants exhibited better adaptation against major abiotic stresses such as drought, high VPD, heat, and cold stresses by virtue of enhanced transpiration efficiency, it has the potential to engineer abiotic stress tolerance for sustained growth and productivity of crops.</p>