Manuscrito
Stress gene expression analysis in a tolerant maize landrace in response to combined salt and boron stress
Autor
Huanca-Mamani, Wilson Alfredo
Vargas-Ortíz, Marcelo Felipe
Cárdenas-Ninasivincha, Steffany Francesca
Acosta-Garcia, Gerardo
Bastias, Elizabeth
Institución
Resumen
To understand the molecular stress response in maize plants under high salt and boron (B) stress, we
focused on the transcript accumulation of six stress-related genes in Lluteño maize, a sweet corn
landrace from the Lluta valley (northern Chile), tolerant to salt and B stress. Lluteño maize and a
maize hybrid B73 seedlings were exposed to 150 mM NaCl and 20 ppm B in nutrient solution for
120 hrs, then roots and leaves samples were collected and Na+ and B concentration were
determined. Transcript accumulation of three salt stress-related genes SOS1, NHX2 and HKT1 and
three B stress-related genes BOR1, BOR2 and PIP1;2 were determined in roots and leaves of
Lluteño maize at 3 and 96 h after stress, using RT-PCR and real-time PCR. The results indicated
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that combined salt and B stress caused physiological parameter changes. The damage was more
severe in B73 than in Lluteño maize, confirming that this landrace behaves as a plant tolerant to
these stresses. Regulation of stress-related genes under combined stress was different than under
individual stresses. The ability of Lluteño maize to survive and thrive in soil with high salinity and
B concentration is probably based on decrease membrane water permeability preventing the salt and
B uptake from the roots through down-regulation of BOR1, BOR2 transporters and PIP1;2
aquaporin. The restriction of the B movement and accumulation in aerial parts through downregulation
of BOR1, BOR2 transporters. The increase water transport mediated by the up-regulation
of the PIP1;2 in leaves, allowing cellular water conservation, and the retrieval of Na+ from xylem
through up-regulation of HKT1;1 transporters in roots and leaves.
Key words: Salt tolerance, boron tolerance, Lluteño maize, SOS1, NHX2, HKT1;1, BOR1, BOR2,
PIP1;2.
Abbreviations: BOR_boric acid/borate transporters; HKT_high-affinity K+ transporter; KIRC_K+
inward-rectifying channel; KORC_K+ outward-rectifying channel; NHX1_Na+/H+ antiporter 1;
PIP_Plasma membrane intrinsic protein; SOS1_salt overly sensitive 1. 24