Content area
Full Text
Plant Mol Biol Rep (2013) 31:12931304 DOI 10.1007/s11105-013-0587-y
ORIGINAL PAPER
Involvement of Ca2+ and CaM3 in Regulation of Thermotolerance in Lily (Lilium longiflorum)
Xing Cao & Jin Yi & Ze Wu & Xian Luo & Xionghui Zhong &
Jian Wu & Muhammad Ali Khan & Yang Zhao & Mingfang Yi
Published online: 8 May 2013# Springer Science+Business Media New York 2013
Abstract Involvement of calcium (Ca2+) and different calmodulin (CaM) isoforms in heat shock (HS) signal transduction in lily (Lilium longiflorum) was investigated in this study. Application of CaCl2 enhanced the thermotolerance of lily, whereas treatment with calcium ion chelator EGTA and CaM antagonist trifluoperazine (TFP) lowered the thermotolerance. Besides, HS-induced expression of LlHsf1 and LlHsfA2 genes were up-regulated by CaCl2 and down-regulated by EGTA or TFP. These findings implied that Ca2+CaM were involved in HS signal transduction in lily via HSF pathway. Subsequently, five LlCaM genes encoding three canonical CaM isoforms were isolated and characterized, among which the LlCaM3 expression was induced by heat and CaCl2 and correlated positively with thermotolerance of lily. Additionally, transient expression analysis determined LlCaM3 to be a cytoplasm and nucleus protein. Furthermore, overexpression of LlCaM3 in Arabidopsis (Arabidopsis thaliana) increased the transcript level of AtHsfA1a and AtHsp18.2 following HS and improved the thermotolerance of transgenic plants. Taken together, the results suggest that LlCaM3 is a key component in Ca2+CaM HS
signaling pathway in lily and may be in the upstream of HSF.
Keywords Lilium longiflorum . Calmodulin . Calcium . Heat shock transcription factor . Heat stress . Thermotolerance
Introduction
Transient elevation in temperature, usually 1015 C above the optimum, is generally taken as heat stress or heat shock (HS) which is one of the key environmental stresses in the fields around the world (Wahid et al. 2007; Xin et al. 2010). HS causes an array of physiochemical and morpho-anatomical changes in plants, which affect plant growth and development and may bring about a severe decline in economic yield (Wahid et al. 2007). As sessile organisms, plants have evolved a variety of defense mechanisms against unavoidable HS, one of which is the synthesis and accumulation of heat-shock proteins (HSPs) (Fu et al. 2010). HSPs function as molecular chaperones, playing a crucial role in maintaining cellular homeostasis by assisting cellular...