Organic nitrogen metabolism of crucifer seedlings in relation to their responses towards Xanthomonas campestris pv. campestris

Abstract

Summary Diminution or increase in the amount of protein in the tissue extracts of bacterium-inoculated crucifer seedlings was parallel to the enhanced or diminished protease activities. The invariable loss or occasional accretion of amino acid constituents in such tissues were irrespective of the utilization or build up of protein. Breakdown of protein, enhanced protease activity and concurrent accumulation of amino acids in excess of that nutritionally utilized by the bacteria were detected in root, stem and leaf tissue extracts of susceptible cauliflower cvs. “Dania”, “Pusi”, “Pusa Deepali”, Kohlrabi cv. “Early Vienna” and mustard cv. “Baruna” after 7, 9, 11, 13 and 15 days of infection of Xanthomonas campestris pv. campestris. Exclusive amino acids present during susceptible response alone, were leucine/isoleucine (cauliflower cv. “Pusa Deepali”), serine (cauliflower cv. “Pusi”; mustard cv. “Baruna”) and proline (Kohlrabi cv. “Early Vienna”). Protein accumulation invariably occurred in the root, stem and leaf tissue extracts of the seedlings of resistant cauliflower cv. “Snowball”, Kohlrabi cv. “Earliest White” and mustard cv. “Yellow” at different stages (7, 9, 11, 13 and 15 days) of host-bacterium interaction. There was a concomitant accretion of certain exclusive amino acids as well. These were valine, tyrosine, tryptophan, β-phenyl-alanine and asparagine. However, there were some amino acids namely γ-aminobutyric acid, β-alanine, dl-alanine, glycine and threonine, which accumulated in the tissues of the crucifer seedlings having either susceptible or resistant response.