Article

The HyPRP gene EARLI1 has an auxiliary role for germinability and early seedling development under low temperature and salt stress conditions in Arabidopsis thaliana. Planta

Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Institute of Life Science, Northwest University, Xi'an 710069, Shaanxi, China.
Planta (Impact Factor: 3.26). 05/2011; 234(3):565-77. DOI: 10.1007/s00425-011-1425-9
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ABSTRACT

The effect of the hybrid proline-rich protein (HyPRP) gene EARLI1 on the rate of germination (germinability) of Arabidopsis seeds and seedling growth under low temperature and salt stress conditions was investigated. EARLI1 was induced during germination in embryonic tissues, and was strongly expressed in certain parts of young seedlings. Comparisons of control, overexpressing (OX), and knockout (KO) lines indicated that higher than wild type levels of EARLI1 improved germinability, root elongation, and reduction of sodium accumulation in leaves under salt stress, as well as germinability under low-temperature stress. Abscisic acid (ABA) contents were relatively low after prolonged salt stress, suggesting that EARLI1 has an ABA-independent effect on germinability under these conditions. Overexpression of EARLI1 during germination enhanced the sensitivity of seeds to exogenously applied ABA, suggesting that EARLI1 has an ABA-dependent negative effect on seed germinability under high ABA stress conditions. Well-known stress response marker genes such as COR15a, KIN1, P5SC1, and RD29 were unaffected whereas P5SC2, RD22, or RAB18 were only slightly affected in OX and KO plants. The pleiotropic effects of EARLI1 during stress and an absence of strong regulatory effects on stress marker genes suggest that this HyPRP gene has an auxiliary role for various stress protection responses in Arabidopsis.

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    • "In rice, the presence or absence of the qLTG3-1 gene, controlling low temperature tolerance at the seedling stage, revealed a major effect on the defense and other gene regulons (Fujino and Matsuda, 2010). Overexpression of EARLI1 in Arabidopsis resulted in improved germination, root elongation and reduction of sodium accumulation in leaves under salt stress as well as the germinability under low-temperature stress (Xu et al., 2011). The increased endochitinase levels found in transgenics are plausibly due to the involvement of CcHyPRP as one of the components in the defense signaling cascade. "
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    • "Apparently, neither AZI1 nor EARLI1 deficiency can be fully compensated for by other members of the EARLI or LTP family. Similarly to EARLI1 overexpression (Xu et al., 2011a), elevated AZI1 levels improve salt tolerance. Consequently, hypersensitivity in the mutants is not merely due to an imbalance in the relative amounts of EARLI-type HyPRPs. "
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