The anther-specific protein encoded by the Brassica napus and Arabidopsis thaliana A6 gene displays similarity to β-1,3-glucanases

An anther-specific Brassica napus cDNA, A6, and two corresponding Arabidopsis thaliana genes have been isolated. Sequence analyses of A6 revealed similarity to β-1,3-glucanases. The deduced A6 protein differs from other β-1,3-glucanases in the possession of a long C-terminus. Immunoblotting using an antibody raised to the A6 protein detects a temporal 60 kDa protein in B. napus buds, suggesting that the long C-terminal region is present in the mature protein. A6 promoter—GUS and RNase fusions demonstrate that the A6 gene is tapetum-specific and temporally expressed with a peak in activity when the plant normally expresses callase (a complex of endo- and exo-β-1,3-glucanase activities). The sequence similarity of A6 to other β-1,3-glucanases, coupled with the temporal and spatial expression data, suggests that A6 may be part of the callase enzyme complex.     

钙离子对PSII颗粒放氧活性的影响

外加5 mmol/L Ca~(2 )可以使菠菜PSⅡ颗粒的放氧活性增高。PSⅡ颗粒经EGTA透析、低pH值、光照、2 mol/L NaCl等处理后,放氧活性下降,同时,这些颗粒的钙含量也相应降低。但当外加 5 mmol/L Ca~(2 )时,可使这些颗粒全部或部分地恢复放氧活性。PSⅡ颗粒中存在的钙对放氧起着重要作用;钙在PSⅡ颗粒中的结合位点不止一个,其结合状态有紧密和松散之别。