Characterization and Evaluation of Transgenic Rice Pyramided with the Pi Genes Pib, Pi25 and Pi54

• Published in: Rice (New York, N.Y.) Vol. 14; no. 1; p. 78
• Main Authors: Peng, Meifang, Lin, Xiaomin, Xiang, Xiaoli, Ren, Huibo, Fan, Xiaoli, Chen, Kegui
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-12-2021; Springer Nature B.V; SpringerOpen
• Subjects: Agriculture; Biomedical and Life Sciences; Blast disease; Crop yield; Cultivars; Disease resistance; Flowering; Gene expression; Genes; Genomes; Impact resistance; Life Sciences; Magnaporthe oryzae; Marker-assisted selection; Next Generation Rice Disease Research; O. sativa; Original; Original Article; Pathogens; Pi25; Pi54; Pib; Plant breeding; Plant Breeding/Biotechnology; Plant Ecology; Plant Genetics and Genomics; Plant growth; Plant Sciences; Rice; Transcription; Transgenes; Transgenesis; Transgenic plants; Blast disease; Gene pyramiding; RNA-Seq; Transgenesis; Transcriptome
• ISSN: 1939-8425; 1939-8433; 1934-8037
• DOI: 10.1186/s12284-021-00512-w

Background
Emergence of new pathogen strains of
Magnaporthe oryzae
is a major reason for recurrent failure of the resistance mediated by a single resistance gene (
Pi
) in rice. Stacking various
Pi
genes in the genome through marker-assisted selection is thus an effective strategy in rice breeding for achieving durable resistance against the pathogen. However, the effect of pyramiding of multiple
Pi
genes using transgenesis still remains largely unknown.
Results
Three
Pi
genes
Pib
,
Pi25
and
Pi54
were transferred together into two rice varieties, the
indica
variety Kasalath and the
japonica
variety Zhenghan 10. Transgenic plants of both Kasalath and Zhenghan 10 expressing the
Pi
transgenes showed imparted pathogen resistance. All the transgenic lines of both cultivars also exhibited shorter growth periods with flowering 2–4 days early, and shorter plant heights with smaller panicle. Thus, pyramiding of the
Pi
genes resulted in reduced grain yields in both rice cultivars. However, tiller numbers and grain weight were generally similar between the pyramided lines and corresponding parents. A global analysis of gene expression by RNA-Seq suggested that both enhancement and, to a lesser extent, inhibition of gene transcription occurred in the pyramided plants. A total of 264 and 544 differentially expressed genes (DEGs) were identified in Kasalath and Zhenghan 10, respectively. Analysis of the DEGs suggested that presence of the
Pi
transgenes did not alter gene expression only related to disease resistance, but also impacted many gene transcriptions in the pathways for plant growth and development, in which several were common for both Kasalath and Zhenghan 10.
Conclusion
Pyramiding of the
Pi
genes
Pib
,
Pi25
and
Pi54
via transgenesis is a potentially promising approach for improving rice resistance to the pathogen
Magnaporthe oryzae
. However, pleiotropic effects of the
Pi
genes could potentially result in yield loss. These findings support the idea that immunity is often associated with yield penalties. Rational combination of the
Pi
genes based on the genetic background may be important to balance yield and disease resistance.