Enhanced Resistance to Seed-Transmitted Bacterial Diseases in Transgenic Rice Plants Overproducing an Oat Cell-Wall-Bound Thionin

Abstract

Bacterial attack is a serious agricultural problem for growth of rice seedlings in the nursery and field. The thionins purified from seed and etiolated seedlings of barley are known to have antimicrobial activity against necrotrophic pathogens; however, we found that no endogenous rice thionin genes alone are enough for resistance to two major seed-transmitted phytopathogenic bacteria, Burkholderia plantarii and B. glumae, although rice thionin genes constitutively expressed in coleoptile, the target organ of the bacteria. Thus, we isolated thionin genes from oat, one of which was overexpressed in rice. When wild-type rice seed were germinated with these bacteria, all seedlings were wilted with severe blight. In the seedling infected with B. plantarii, bacterial staining was intensively marked around stomata and intercellular spaces. However, transgenic rice seedlings accumulating a high level of oat thionin in cell walls grew almost normally with bacterial staining only on the surface of stomata. These results indicate that the oat thionin effectively works in rice plants against bacterial attack.

Burkholderia glumae en el cultivo de arroz en Costa Rica.

“…En el arroz esta bacteria causa la enfermedad conocida como añublo bacterial de la panícula del arroz, que es de gran impacto económico en diferentes partes del mundo, provocando pérdidas de hasta un 40% de la producción (Iwai et al, 2002;Rush et al, 2003). Además, esta especie es causante del marchitamiento en muchos cultivos de campo como tomate, chile, berenjena, papa, girasol (Uematsy et al, 1976).…”

Genetic studies of transgenic rice plants overproducing an antibacterial peptide show that a high level of transgene expression did not cause inferior effects on host plants

“…Chiyohonami) line CT2, which expressed Asthi1 (an oat thionin gene) and hph (a hygromycn resistance gene) by a strong constitutive promoter E7WI and by improved CaMV 35S promoter, respectively (Mochizuki et al 1999;Iwai et al 2002). The seedlings of T4, homozygous on Asthi1 and hph, were grown in isolated paddy field in 2001 at Joetsu city, Japan (Yatou et al 2003) and selfed to obtain T5.…”

“…However, a high level of ectopic foreign gene expression is thought to cause inferior effects such as disturbance of basal metabolism and altered expression of endogenous genes similar to transgene in host plants. Because the information on the effect of high level of transgene expression is limited, studies on the altered characteristics in transgenic plant and its genetic inheritance are absolutely needed.Using Agrobacterium-mediated transformation method, we have previously generated hygromycinresistant 41 individual transgenic rice plants (T0) in which an oat cell wall-bound thionin gene (Asthi1) was expressed under the control of a strong promoter E7WI: seven tandem repeats of the 0.2 kb Califlower mosaic virus (CaMV) 35S enhancer (E7), the omega sequence from Tobacco mosaic virus and the 1st intron of phaseolin gene in pE7133 (Iwai et al 2002). The promoter conferred 70-fold higher expression compared with the 35S promoter in pBI221 in rice protoplasts (Mitsuhara et al 1996).…”

“…Using Agrobacterium-mediated transformation method, we have previously generated hygromycinresistant 41 individual transgenic rice plants (T0) in which an oat cell wall-bound thionin gene (Asthi1) was expressed under the control of a strong promoter E7WI: seven tandem repeats of the 0.2 kb Califlower mosaic virus (CaMV) 35S enhancer (E7), the omega sequence from Tobacco mosaic virus and the 1st intron of phaseolin gene in pE7133 (Iwai et al 2002). The promoter conferred 70-fold higher expression compared with the 35S promoter in pBI221 in rice protoplasts (Mitsuhara et al 1996).…”

“…Plant Biotechnology 23, 63-69 (2006) (Iwai et al 2002). One of T3 plants (designated CT2-1-4-6, homozygous) was selected, and its seeds (T4) were sowed and grown in an isolated paddy field to evaluate agronomic traits and environmental risk (Yatou et al 2003).…”