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
Source: PubMed


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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    ABSTRACT: In this study, we report the overexpression of Cajanus cajan hybrid-proline-rich protein encoding gene (CcHyPRP) in rice which resulted in increased tolerance to both abiotic and biotic stresses. Compared to the control plants, the transgenic rice lines, expressing CcHyPRP, exhibited high-level tolerance against major abiotic stresses, viz., drought, salinity and heat, as evidenced by increased biomass, chlorophyll content, survival rate, root and shoot growth. Further, transgenic rice lines showed increased panicle size and grain number compared to the control plants under different stress conditions. The CcHyPRP transgenics, as compared to the control, revealed enhanced activities of catalase and superoxide dismutase (SOD) enzymes and reduced malondialdehyde (MDA) levels. Expression pattern of CcHyPRP::GFP fusion-protein confirmed its predominant localization in cell walls. Moreover, the CcHyPRP transgenics, as compared to the control, exhibited increased resistance to the fungal pathogen Magnaporthe grisea which causes blast disease in rice. Higher levels of bZIP and endochitinase transcripts as well as endochitinase activity were observed in transgenic rice compared to the control plants. The overall results demonstrate the intrinsic role of CcHyPRP in conferring multiple stress tolerance at the whole-plant level. The multipotent CcHyPRP seems promising as a prime candidate gene to fortify crop plants for enhanced tolerance/resistance to different stress factors.
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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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    ABSTRACT: A plant(')s capability to cope with environmental challenges largely relies on signal transmission through mitogen-activated protein kinase (MAPK) cascades. In Arabidopsis thaliana, MPK3 is particularly strongly associated with numerous abiotic and biotic stress responses. Identification of MPK3 substrates is a milestone towards improving stress resistance in plants. Here, we characterise AZI1, a lipid transfer protein (LTP)-related hybrid proline-rich protein (HyPRP) as a novel target of MPK3. AZI1 is phosphorylated by MPK3 in vitro. As documented by co-immunoprecipitation and bimolecular fluorescence complementation experiments, AZI1 interacts with MPK3 to form protein complexes in planta. Furthermore, null mutants of azi1 are hypersensitive to salt stress, while AZI1 overexpressing lines are markedly more tolerant. AZI1 overexpression in the mpk3 genetic background partially alleviates the salt-hypersensitive phenotype of this mutant, but functional MPK3 appears to be required for the full extent of AZI1-conferred robustness. Notably, this robustness does not come at the expense of normal development. Immunoblot and RT-PCR data point to a role of MPK3 as positive regulator of AZI1 abundance.
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    • "When ethanol volatilized completely (10 h), soil water content was adjusted to 60 % water holding capacity. After all the dishes were placed in greenhouse (28 °C) for 48 h, 30 surface-sterilized (Xu et al. 2011) seeds were put in each dish. To assess surface sterility, 100 μL aliquots of the final-rinse water were spread on nutrient agar. "
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