Targeting genes for ion homeostasis and salt tolerance in finger millet (Eluesine coracana (L) Gaertn. ): Over-expressing genes for salt compartmentation and proton gradient generation and their significance in salt tolerance
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Date
2013-12-12
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University of Agricultural Sciences, Bengaluru
Abstract
Salinity in agricultural terms is the excess of salts above the level plant requirement.
Most often it poses constraints in the growth hence productivity of the crop plants gets
affected and therefore is a serious concern. Salinity is one of the major abiotic stresses
affecting plant productivity. Finger millet (Eluesine coracana (L.)Gaertn), is grown on
over 4 million hectare worldwide and it is a primary food for millions in dry lands and
is sensitive to moderate levels of salt in the soil.
To generate finger millet plants that can adapt to saline soil, AVP1, a vacuolar H+-pyrophosphatase
gene from Arabidopsis thaliana, and PgNHX1, a vacuolar
Na+/H+antiporter gene from Pennisetum glaucum, were co-expressed by Agrobacterium
tumefaciens-mediated transformation and attempts has been made on standardization of
an efficient direct regeneration protocol in finger millet. The shoot meristem was found
to be the best responsive explants for direct organogenesis. The functional significance
of AVP1, NHX1 and AVP1::NHX1 transgenic plants was demonstrated invitro and
invivo by using Hydroponics’ systems, gravimetric analysis and soil system by Karnal
method. Physiological studies such as CMS, Nutrient estimation of Na, K, and Ca,
chlorophyll stability index, Standard Evaluation Score for visual salt injury, Proline, OA
and yield analysis. It is reported here that co-expression of AVP1 and PgNHX1 confers
enhanced salt tolerance to the transformed finger millet compared with the AVP1 and
PgNHX1 single gene transgenic plants and the wild-type. These transgenic plants grew
well in the presence of 20 dS/m NaCl while wild-type plants exhibited chlorosis and
died within the 30days.The physiological analysis of the transgenic lines clearly
demonstrates that co-expression of AVP1 and PgNHX1 improved the osmoregulatory
capacity of double transgenic lines by enhanced sequestration of ions into the vacuole
from cytosolby increasing the availability of protons and thus alleviating the toxic effect
of Na+
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Keywords
planting, millets, transgenics, genes, tolerance, food preservation, genetic processes, vegetative propagation, regeneration, thinning