Molecular Cloning and Functional Analysis of a Novel Type of Bowman-Birk Inhibitor Gene Family in Rice

Abstract

inhibitor (BBI) genes encode serine protease inhibitors that have repetitive cysteine-rich domains with reactive sites for the trypsin or chymotrypsin family. We have identified seven BBI genes from japonica rice (Oryza sativa subsp. japonica var Teqing). All of the genes identified were found in a single cluster on the southern end of the long arm of rice chromosome 1. Four of the seven BBI genes have two repetitive cysteine-rich domains, whereas one has a truncated domain with only one reactive site. We have also identified three novel BBI genes, each of which possesses three repetitive domains instead of two. In situ hybridization analyses indicated that the accumulation of rice BBI transcripts was differentially regulated in germinating embryos and also in the leaves, roots, and flower organs at later developmental stages. Different members of the rice BBI gene family displayed different expression patterns during rice seed germination, and wounding induced the expression of rice BBI transcripts. The three-domain BBIs had higher expression levels than the two-domain BBIs. It was also found that the mRNA of rice BBI genes was present in abundant amounts in scutellar epithelium and aleurone layer cells. RBBI3-1, one of the three-domain RBBI, exhibited in vitro trypsin-inhibiting activity but no chymotrypsin-inhibiting activity. Overexpression of RBBI2-3 in transgenic rice plants resulted in resistance to the fungal pathogen Pyricularia oryzae, indicating that proteinase inhibitors confer resistance against the fungal pathogen in vivo and that they might play a role in the defense system of the rice plant.Plants have developed defense systems to combat various pathogens throughout their life cycle, from the seed stage until senescence, and it is particularly important that the embryo be kept free from infection. There are several embryonic defense mechanisms, including the production of plant lectins and pathogen-related proteins in response to attacks by pathogens or insects (Swegle et al., 1992;Ye et al., 2001;Guiderdoni et al., 2002). A well-known defense component is Ser protease inhibitors. They are expressed in developing seeds and are thought to play an important role in inhibiting trypsin and chymotrypsin of external origin (Ryan, 1981). Two major Ser protease inhibitors have been studied extensively in plants: Kunitz inhibitors and Bowman-Birk inhibitors (BBIs; Ryan, 1990). BBIs are Cys-rich proteins of about 8 to 16 kD with disulfide bonds and are encoded by a family of related genes. The BBI gene family has been found in both the Fabaceae and the Poaceae. BBIs identified in Fabaceae, such as soybean (Glycine max) and lima bean (Phaseolus lunatus), are 8-kD proteins. They have one BBI domain with two reactive sites for trypsin and the related enzymes, such as chymotrypsin (Birk, 1987). These protease inhibitors are double-headed, with two reactive sites in a single inhibitor molecule. Interestingly, this type of inhibitor displays anticarcinogenic activity (Birk, 1993;Kennedy, 1993).The BBIs found in...

Machine Learning Approaches Distinguish Multiple Stress Conditions using Stress-Responsive Genes and Identify Candidate Genes for Broad Resistance in Rice

“…There were three annotation clusters with enrichment scores greater than 2.0 in the conserved up-regulated gene set related to heat shock protein Hsp20, Val, Leu, and Ile degradation, and the BowmanBirk proteinase inhibitor family of Ser protease inhibitors. In rice, Bowman-Birk proteinase inhibitor genes were reported previously to be induced in multiple stresses like wounding, infection, and hormonal stress (Rakwal et al, 2001;Qu et al, 2003). The top annotation clusters in the nonconserved abiotic down-regulated and biotic up-regulated gene set were made up of a number of interpro domain terms, glycoprotein, metal-ion binding, plant peroxidases (POXs), and glycoside hydrolases.…”

Salicylic acid and ethylene signaling pathways are involved in production of rice trypsin proteinase inhibitors induced by the leaf folder Cnaphalocrocis medinalis (Guenée)

“…Moreover, some plant PIs specifically inhibit the proteases of pathogens [6,7]. Therefore, PIs are regarded as an essential part of the plant's natural defense system against pests [8][9][10].…”

“…The induced PIs represent either local [7,17] or systemic [18][19][20][21] responses, and either age-dependent [22] or organ-specific [8,18] traits. Application of chemical signals, such as jasmonic acid (JA), abscisic acid (ABA) and ethylene or salicylic acid (SA) can manipulate the production of PIs in plants [13,14,23,24], but the effects of each compound differ for different PIs.…”

A Review: Biological and Technological Functions of Barley Seed Pathogenesis-Related Proteins (PRs)

“…The homologous protein WBBI, from wheat seed, shows a strong antifungal activity against a number of pathogenic fungi and inhibits fungal trypsin-like activity 59 . Overexpression of RBBI from rice in transgenic plants resulted in resistance to the fungal pathogen Pyricularia oryzae, confirming that cereal BBIs confer resistance against the fungal pathogen in planta 267 . In addition, involvement of WBBI in the tolerance of salt stress has been confirmed 303 .…”