title: Lily ASR protein-conferred cold and freezing resistance in Arabidopsis.
abstract: The lily LLA23 protein is a member of the abscisic acid, stress and ripening-induced (ASR) protein family. Constitutive overexpression of LLA23 under the cauliflower mosaic virus 35S promoter confers cold and freezing tolerance in Arabidopsis. The phenotypical growth and survival percentage of the two transgenic 35S::LLA23 plants showed higher resistance to cold and freezing conditions than those of wild-type (WT) plants. The electrolyte leakage in WT leaves increased by approximately fourfold at -2 °C relative to that at 22 °C whereas both transgenic leaves showed little ion leakage under the same conditions. A microarray analysis of LLA23-overexpressing transgenic line, 35S::LLA23E, under normal growing conditions was previously conducted by Yang et al. (Protoplasma, 2008, 233:241-254). Microarray analysis showed that 12 cold-responsive genes are upregulated and 25 cold-responsive genes are downregulated by lily ASR. Many ASR-regulated genes encode proteins involved in the classes of defense/stress-related, transcription, and metabolism. Quantitative polymerase chain reaction analysis confirms the changes in mRNA levels observed in the microarray analysis. Thus, our results provide in vivo evidence implying that LLA23 mediates cold/freezing stress-responsive signaling. To gain further insight into the functions of LLA23 protein, an in vitro enzyme protection assay was used in which lactate dehydrogenase and malate dehydrogenase were subjected to unfavorable conditions. The assay revealed that both enzyme activities were significantly retained with the addition of LLA23, which was superior to either trehalose or BSA, suggesting that the LLA23 protein can protect enzymatic activities against freeze-thaw cycles. The 35S::LLA23 seedlings also exhibited enzyme activity superior to WT at -4 °C. These results suggest that LLA23 may act as an osmoprotectant as well as a transcription factor to confer 35S::LLA23 plants enhanced cold and freezing resistance.
authors.affiliation: Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan.
authors.forename: Yi-Feng
authors.initials: YF
authors.lastname: Hsu
authors.forename: Shu-Chuan
authors.initials: SC
authors.lastname: Yu
authors.forename: Chin-Ying
authors.initials: CY
authors.lastname: Yang
authors.forename: Co-Shine
authors.initials: CS
authors.lastname: Wang
mesh_terms: D000064:Acclimatization / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D058639:Cold-Shock Response / Q000235:genetics*; D005615:Freezing; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D027762:Lilium / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018749:RNA, Plant / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics
chemical_list: C413484:LLA23 protein, Lilium longiflorum; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant