A cDNA clone of the maize a tubulin --M. Mereghetti, G. Consonni and C. Tonelli
 
 
The a and b tubulins of most eukaryotes are encoded by small gene families (Cleveland and Sullivan Annu. Rev. Biochem. 54:331, 1985). A comparison of the amino acid sequences of the a and ß tubulins from numerous species suggests that the tubulins are extensively conserved in evolution.

In plants the a and b tubulin genes of Arabidopsis (Ludwig et al., Proc. Natl. Acad. Sci. 84:5833, 1987) and soybean (Guiltinan et al., Plant Mol. Biol. 10:171, 1987) have been cloned by cross-hybridization with Chlamydomonas reinhardtii tubulin probes (Silflow et al., Mol. Cell Biol. 5:2389, 1985) respectively.

In an attempt to clone the a tubulin of maize a cDNA library was established in lambda gt10 from poly(A)+ RNA of scutellar nodes and mesocotyls of the W22 inbred line. This library was screened with a-1 tubulin gene of Chlamydomonas (Brunke et al., Nucl. Acid. Res. 10:1295, 1982; kindly provided by B. Burr) and a few positive recombinant phages were isolated. One of them containing a 1 Kb insert was further purified, subcloned in pBSKS (Stratagene), named pCTM5 and used in Southern and Northern analysis.

Genomic DNA of the W22 line was restricted with different enzymes, analyzed by Southern blot and hybridized to the 1 Kb cDNA probe using high stringency conditions. Between four and six bands of hybridization are observed depending on the type of restriction enzyme used. Further analysis is underway in order to estimate the number of a tubulin genes present in the maize genome.

To investigate the expression of the a tubulin genes different tissues have been analyzed. Total RNAs isolated from endosperms at 20 DAP, mesocotyls and scutellar nodes, roots, coleoptiles, leaves, anthers, pollen and silks were analyzed by Northern blot and hybridized to the 1 Kb probe. A single band of approximately 1.5 Kb was observed in each sample. These results indicate that mRNAs homologous to our cDNA probe are present in all tissues analyzed and share the same size.


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