BOWMAN-BIRK PROTEASE INHIBITOR GENE EXPRESSION IN PHASEOLUS VULGARIS – ORGAN SPECIFICITY AND INDUCTION UNDER ABIOTIC STRESSES
IRINA I. VASEVA1, KAMELIA IVANOVA2, LYUDMILA SIMOVA-STOILOVA1*
1 Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. Georgi Bonchev Str., bl. 21, 1113, Sofia, Bulgaria.
2 Sofia University St. Kliment Ohridski, Faculty of Biology, 8, Dragan Tsankov Blvd., 1164, Sofia, Bulgaria
* Corresponding author: lsimova@mail.bg
Keywords: drought, gene expression, legume, protease inhibitors, salt stress
Abstract: Seeds of legume plants are rich in serine protease inhibitors - up to 10% of grain protein content, mainly Bowman-Birk (BBI) and Kunitz types. However, data about the presence of protease inhibitors in tissues other than seeds and their induction under abiotic stress are scarce. We analyzed the organ-specific expression of three Phaseolus vulgaris genes for BBI inhibitors with published complete sequences in the NCBI database: PHAVU_004G133900g (ID: 18632939), PHAVU_004G134100g (ID: 18632941), and PHAVU_004G134000g (ID: 18632940) in two Bulgarian common bean cultivars – Ustrem and Blian, testing young, fully expanded and senescing leaves, roots, flowers and pods. Senescing leaves and roots had elevated expression of BBI genes as compared to fully expanded leaves, flowers and pods, especially in cv. Ustrem. The BBI transcript profiling was further assessed in the second trifoliate leaves and roots of cv. Ustrem, subjected to osmotic stress of -0,6 MPa in the nutrient solution, exerted by PEG 6000 or NaCl, with different duration. Relatively weak changes in the expression profiles of the three BBI genes were documented under the applied stresses with different tendencies depending on the gene, the stress type and its duration. Long-term PEG stress upregulated PHAVU_004G133900g and PHAVU_004G134100g but downregulated PHAVU_004G134000g expression in the leaves. The expression of the three genes in the roots was inhibited by the treatment. A slight increase in PHAVU_004G134000g transcript levels was measured in salt-stressed leaves after short-term exposure. The results reveal that abiotic stresses provoke organ-specific dynamic changes in the expression of the studied BBI gene.