Abstract
Bowman-Birk inhibitor (BBI) is a soybean seed serine protease inhibitor whose nutraceutical properties far exceed its anti-nutritional property arising from its trypsin and chymotrypsin inhibitor activity. High BBI soybean genotypes are sought for the commercial preparation of this nutraceutical biomolecule while low BBI content in Kunitz trypsin inhibitor (KTI)-free genetic background is desirable in soymeal manufacturing. In the present investigation, monoclonal antibody assay of 95 soybean genotypes revealed 11-fold genetic variation for BBI concentration. The study led to the identification of 3 very high (>20 mg/g defatted soy flour) and 5 very low BBI (< 4 mg/g defatted soy flour) soybean genotypes. Contribution of BBI to total trypsin inhibition activity ranged from 2.2 to 53.5% with average value of 11.6%. Genotypes with varying level of BBI raised consecutively for two years exhibited non-significant (p>0.05) effect of growing year on the trait. BBI content in BC3F2 derived KTI-free lines was at par with the recurrent parent. Low and high BBI content genotypes with diverse genetic background identified in the study may be exploited to develop mapping population to identify genomic regions underlying BBI in soybean.
Highlights
Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI) are two major serine protease inhibitors in soybean seeds, accounting for nearly 6% fraction of total soluble protein
Range of 9.4-11.0 mg/g defatted soy flour for BBI concentration was noted among these 5 recombinant lines, thereby showing increase in BBI content compared to recurrent parent (7.4 mg/g defatted soy flour) but this increase was statistically not significant (p>0.05)
It would be interesting to investigate which isoforms correspond to low and high BBI content genotypes identified in the present study and exploit the information in designing breeding programme for developing novel high and low BBI soybean genotypes. This is the first report pertaining to the estimation of BBI in large number of soybean genotypes to assess its genetic variation and contribution to total trypsin inhibitor activity (TIA)
Summary
Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI) are two major serine protease inhibitors in soybean seeds, accounting for nearly 6% fraction of total soluble protein. KTI, 21 kDa polypeptide with 181 amino acids, is an anti-nutritional factor (ANF) in soybean seeds as it inhibits trypsin to the magnitude of 2.51 times of its own concentration (Kumar et al, 2018), thereby interfering with the digestion of proteins in human gastrointestinal tract (GIT). Various physical and biological methods, namely, boiling, autoclaving, pulse electric field, microwave irradiation and sprouting are being used by soy industries for the inactivation of this ANF (Dia et al, 2012; Chen et al, 2014; Kumar et al, 2019). Received in revised form: 18 Feb 2021. From Volume 13, Issue 1, 2021, Notulae Scientia Biologicae journal will use article numbers in place of the traditional method of continuous pagination through the volume
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