CsPDC-E1α, a novel pyruvate dehydrogenase complex E1α subunit gene from Camellia sinensis, is induced during cadmium inhibiting pollen tube growth.

Cadmium (Cd) is one of the most toxic heavy metal pollutants highly hazardous to pollen tubes by disrupting mitochondria. Mitochondrial pyruvate dehydrogenase complex (PDC) plays important roles in cellular metabolism and links cytosolic glycolytic metabolism to the tricarboxylic acid cycle (TCA). However, the relationship between PDC and pollen germination and pollen tube growth under Cd stress remains unclear. Here we found that Cd inhibited Camellia sinensis pollen germination and pollen tube growth in a dose dependent manner and disrupted the tip clear zone of pollen tube. Furthermore, we isolated a novel PDC gene (CsPDC-E1α) from C. sinensis. The full-length cDNA of CsPDC-E1α was 1606 bp and encoded a 393-amino acid protein containing typical PDC TPP-binding site, heterodimer interface, phosphorylation loop region and tetramer interface domain, suggesting that CsPDC-E1α was a member of the PDC_ADC_BCADC subfamily in thiamine pyrophosphate (TPP) family. Bioinformatics analysis indicated that the CsPDC-E1α protein shared high degree of homology with that from Petunia x hybrid. The CsPDC-E1α relative expression levels in pollen were significantly higher than other tissues of C. sinensis, indicating that CsPDC-E1α expression is tissue-specific. To confirm the functions of CsPDC-E1α in pollen response to Cd stress, we analyzed the relative expression level of CsPDC-E1α in Cd-treated pollen tubes and found that the expression of CsPDC-E1α was induced by Cd stress. All these results indicate that CsPDC-E1α might be associated with Cd inhibition of C. sinensis pollen germination and pollen tube growth.