Cloning and functional characterization of β-1, 3-glucanase gene from Podophyllum hexandrum - a high altitude Himalayan plant.

Podophyllum hexandrum is a high-altitude medicinal plant exploited for its etoposides which are potential anticancer compounds. ß-1, 3-glucanase cDNA was cloned from the germinating seeds of Podophyllum (Ph-glucanase). Glucanases belong to pathogenesis related glycohydralase family of proteins, which also play an important role in endosperm weakening and testa rupture during seed germination. Analysis of cloned nucleotide sequence revealed Ph-glucanase with an open reading frame of 852bp encoding a protein of 283 amino acids with a molecular mass of 31kDa and pI of 4.39. In-silico structure prediction of Ph-glucanase showed homology with that of Hevea brasiliensis (3em5B). Structural stability and enhanced catalytic efficiency in harsh climatic conditions possibly due to the presence of glycosyl hydrolase motif (LGIVISESGWPSAG) and a connecting loop towards inner side and well exposed carbohydrate metabolism domain-COG5309, can readily hydrolyse cell wall sugar moieties. Seeds from the transgenic Arabidopsis plants over-expressing Ph-glucanase showed better germination performance against a wide range of temperatures and abscisic acid (ABA) stress. This can be attributed to the accumulation of Ph-glucanase at both transcript and protein levels during the seed germination in transgenic Arabidopsis. Results confirm that the cloned novel seed specific glucanase from a cold desert plant Podophyllum could be used for the manipulation of different plant species seeds against various harsh conditions.