Inheritance of the Absence of the Kunitz Trypsin Inhibitor in Seed Protein of Soybeans¹

Abstract

Soybean [Glycine max (L.) Merrill] seds from reciprocal crosses of ‘Amsoy 71’ and P.I. 157440, reciprocal crosses of P.I. 196172 and P.I. 157440, and the cross P.I. 157440 ✕ ‘Jefferson’ were analyzed using polyacrylamide gel electrophoresis to study the inheritance of the absence of the Kunitz trypsin inhibitor (SBTI‐A2). Amsoy 71 has the SBTI‐A2, at Rf 0.79 (Tia), Jefferson at Rf 0.75 (Tib), P.I. 196172 at Rf 0.83 (Tic), and P.I. 157440 lacks the SBTI‐A2, band. The F2 and F3 data establish that the absence of the SBTI‐A2, band is inherited as a recessive to the codominant alleles Tia, Tib, and Tic. The allele for absence of the SBTI‐A2 band is designated ti. The homozygous recessive condition (ti ti) results in the lack of SBTI‐A2. The lack of the SBTI‐A2, protein was confirmed using spectrophometric assay procedures.

Isolation and Characterization of Messenger RNAs for Seed Lectin and Kunitz Trypsin Inhibitor in Soybeans

“…In addition to substantial biochemical data for these two seed proteins, lectin and trypsin inhibitor have been defined by classical genetic analyses and soybean varieties which lack detectable SBL or SBTI protein have been found (21,22,24). It is the aim of this report and other studies in progress to determine what molecular defects cause the inherited absence of SBL or SBTI protein in certain soybean varieties.…”

A frameshift mutation prevents Kunitz trypsin inhibitor mRNA accumulation in soybean embryos.

“…This natural mutant collection includes varieties that either lack or underproduce Kunitz trypsin inhibitor , seed lectin (Pull et al, 1978), p-amylase (Hildebrand and Hymowitz, 1980), lipoxygenase (Hildebrand and Hymowitz, 1981), glycinin (Scallon, Dickinson, and Nielsen, 1987;Cho et al, 1989), p-conglycinin (Kitamura and Kaizuma, 1981), and urease (Kloth, Polacco, and Hymowitz, 1987). In each inbred lhe, the defect is the result of a mutation that is inherited as a simple Mendelian recessive (e.g., Orf and Hymowitz, 1979). Severa1 seed protein gene mutations have been studied and their molecular lesions have been characterized .…”

“…The KTi-genetic lesion results in a substantial reduction of Kunitz trypsin inhibitor protein and activity in soybean seeds ( Orf and Hymowitz, 1979). We showed recently that KTi' soybean plants contain several Kunitz trypsin inhibitor genes and that these genes are differentially expressed during the soybean life cycle and in transformed tobacco plants (Jofuku, 1987;Jofuku and Goldberg, 1989).…”

Identification and Confirmation of SSR Marker Tightly Linked to the Ti Locus in Soybean [Glycine max (L.) Merr.]

“…These observations fit the expected 3 : 1 ratio for the presence or absence of the SKTI protein band. Earlier studies have shown that the null phenotype of SKTI is inherited as a recessive allele designated ti (Orf and Hymowitz, 1979). The segregation ratios of 3 : 1 observed in the F 2 seed (population 1 and 2) and the Chi-square values strongly suggest that kunitz trypsin inhibitor protein band is controlled by a single recessive gene.…”