Early light induced proteins (ELIPs) are widely distributed in the plant kingdom. Members of the extended light harvesting complex (LHC) superfamily, ELIPs are expressed in the nucleus and the ELIP protein is transiently localized to the thylakoid membranes. Significant increase in expression of ELIPs has been reported in response to stresses such as high light, high and low temperature, exposure to UV and salinity. ELIP expression also increases at transitional stages of chloroplast development such as deetiolation, conversion to chromoplast, and senescence.
In search of cis-regulatory regions, the A. thaliana ELIP1 gene promoter has been investigated in our lab. A double-SORLIP1 element was identified as a critical cis-regulatory region common in the promoters of A. thaliana ELIP1 (At3g22840) and ELIP2 (At4g14690). Point mutations in the double-SORLIP1 element led to significant decline in expression.
Due to the importance of the double-SORLIP1 element, a yeast-one-hybrid assay was set up to find the specific DNA-binding proteins that bind to this region. Light harvesting complex II (LHCA2) and the ortholog of sugar beet HS1 PRO-1 2, heat-shock-like protein 2 (HSPRO2), showed a high specificity in binding to the double-SORLIP1 element. Investigation of lhca2 and hspro2 Arabidopsis mutants did not show any significant difference in high light induced expression of ELIP1 or ELIP2 as compared to wild type. However, the high frequency of LHCA2 clones selected by yeast-one-hybrid assay and the high specificity in binding to the double-SORLIP1 element cannot be ignored.
After reviewing the literature, I hypothesized that LHCA2 may be a new retrograde signal that regulates expression of ELIP genes. However, more experimental evidence is needed to support this proposed function. The potential regulatory role of HSPRO2 is also discussed.
|Commitee:||Gharakhanian, Editte, Malcomber, Simon|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 51/05M(E), Masters Abstracts International|
|Subjects:||Biology, Molecular biology|
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