Molecular cloning and differential expression of sHSP gene family members from the resurrection plant Boea hygrometrica in response to abiotic stresses

Abstract

Small heat shock proteins (sHSPs) are a class of molecular chaperones that bind to and prevent aggregation of proteins. To assess the potential role of sHSPs in protection against abiotic stresses, we conducted a screening of sHSP genes from the desiccation-tolerant resurrection plant Boea hygrometrica, which is widespread in East Asia in alkaline, calcium-rich limestone crevices. In total, 25 sHSP genes, belonging to six subgroups, were identified from the desiccated leaves of B. hygrometrica. Ten of these genes were cloned and named according to the nomenclature proposed for sHSPs. Transcripts of all these BhsHSPs were detectable in fresh leaves, but only 6 genes were induced after desiccation, and remained high during rehydration. Four of the cytosol-targeted BhsHSP genes were up-regulated under treatments, such as heat, cold, alkaline conditions, high calcium, oxidation, or application of the phytohormone abscisic acid. Together, these results demonstrate that CI and CII sHSPs, especially Bh17.9CI and Bh17.4BCII, are associated with abiotic stresses, and may function in the maintenance of protein stability, aiding in the adaptations to extreme environmental conditions in which B. hygrometrica can survive.

Surviving metabolic arrest: photosynthesis during desiccation and rehydration in resurrection plants

“…Out of these, only six genes were upregulated during desiccation and rehydration, and the majority of them were constitutively expressed. 63 Similarly, the constitutive expression of small HSPs in vegetative tissues of C. plantagineum also confirms the preparedness of the plant for desiccation tolerance. 64 While the majority of HSPs accumulate in the cytoplasm, there are also reports suggesting that they accumulate in organelles such as the endoplasmic reticulum, mitochondria, and chloroplasts.…”

“…In B. hygrometrica , 25 small HSP genes belonging to six subgroups were identified. Out of these, only six genes were upregulated during desiccation and rehydration, and the majority of them were constitutively expressed . Similarly, the constitutive expression of small HSPs in vegetative tissues of C. plantagineum also confirms the preparedness of the plant for desiccation tolerance .…”

A comparative study on Ca content and distribution in two Gesneriaceae species reveals distinctive mechanisms to cope with high rhizospheric soluble calcium

“…However, a certain threshold concentration or expression level may limit the role of BhDNAJC2 in B. hygrometrica , for example, high expression of the gene in Arabidopsis can provide higher Ca tolerance than for B. hygrometrica . Giving that the HSP family is composed of a large number of members, and several other HSP genes had been reported to be induced by external Ca application (Zhang et al, 2013 ), further characterization of the interaction of BhDNAJC2 and other HSPs from B. hygrometrica will shine a light to understand the roles of chaperone-mediated protein quality control in the tolerance to high internal Ca in B. hygrometrica .…”

Understanding desiccation tolerance using the resurrection plant Boea hygrometrica as a model system

“…The detached leaves are useful to investigate DT, taking the advantage that these leaves are not affected by interference from developmental regulation and long - distance signaling from other organs during dehydration and rehydration ( Jiang et al, 2007 ). To date, studies using this system have been conducted to characterize the architectural, physiological, cellular, and molecular mechanisms of the DT of B. hygrometrica , revealing dehydration responses such as cell wall folding, accumulation of raffinose oligosaccharides, late embryogenesis abundant (LEA) proteins and small heat shock proteins (sHSPs), antioxidative agents, and enzymes and stabilization of photosynthetic protein-pigment complexes ( Jiang et al, 2007 ; Liu et al, 2009 ; Wang et al, 2009a ; Zhang et al, 2013 ).…”

“…Similarly, sHSPs protect proteins from both aggregation and dehydration by acting as molecular chaperones ( Garrido et al, 2012 ). Ten genes encoding sHSPs were cloned from B. hygrometrica , among which, six cytosol-targeted sHSP coding genes were induced after desiccation and tended to remain highly abundant during rehydration ( Zhang et al, 2013 ). It has been established that stress conditions affect cellular environment at least in part by disturbing protein folding.…”