Cloning And Characterization Of The CDNA Encoding Casein Kinase2 Alpha Subunit From Lily Pollen

Our previous data suggested that the a , p 3 integrin-like proteins be present in lily pollen tube and mediate the interaction between pollen and extracellular matrix of pistil to regulate pollen tube growth. To elucidate further the presense and function of integrin-like protein ,we try to clone 3' terminus seqence of integrin-like gene from germinated pollen of lily by 3' RACE using degenerate primers corresponding to the conserved cytoplasmic regions of a and 3 subunits. However, it proved fruitless athough great efforts have been done. We isolated nine amplified DNA fragments.but none of them is related to the integrin gene.Among these amplified DNA fragments,one clone contains primer sequence but does not translate according to the putitive integrin amino acid sequence. It possess high homology with those of CK2(Casein Kinase 2) a subunits from various species. It is now well established that protein Kinase CK2 is a pleiotropic and abiquitous serine or threonine kinase,which is highly conserved during evolution.We obtained the complete cDNA sequence of CK2 a via 5' RACE. Followed by PCR using two different pairs of primers, we further ascertain the sequence of the coding regions of CK2 a . The complete cDNA sequence of CK2 a from lily pollen contain 999 bp open reading frames, encoding a polypeptide of 333 amino acid and has a predicted molecular weight of 39.2KDa. Sequence analysis of the cDNA showed a high level of homology to the CK2 a from other plant species, for example 90 % homology with Arabidopsis and 94 % homology with maize. It also 76 % homology with human. Moreover, it contains all of the conserved amino acids of CK2 a in various species. The sequence of CK2 a from lily pollen have been deposited in the GeneBank datebase(accession number , AF517838)By PCR, we also proved the persence of two transcripts in germinated lily pollen . The main difference between the two transcripts is lie in the 5'-untranslated region. One is 62bp larger than the other. This region may be jp related to the regulation of protein translation..Anyway, CK2 a cDXA cloning is the first work ever done in plant pollen. It would contribute to understanding the regulation mechanism of pollen tube growth only when more detailed studies of the biochemistry and physiological functions of CK2 had been done in pollen.