Deletion of a Dna K protein gene causes seedling green-revertible albino by retarding chloroplast development in rice

Green-revertible albino mutants are important sources for studying chloroplast structure, chloroplast development, chlorophyll biosynthesis, and plant photosynthesis. In the present study, we characterized a greenrevertible albino mutant gra(k), which was obtained from the tissue-cultured rice Kitaake. The mutant gra(k) exhibited albino on its first three leaves. The leaf color started to turn green at the four-leaf stage. The chlorophyll contents were deeply reduced at the seedling stage, and the chloroplast development was delayed in gra(k). The greenrevertible albino(gra) phenotype of the mutant gra(k) was temperature dependent. The main agronomic traits,including plant height, tilling number per plant, seed setting rate, and thousand-grain weight, slightly decreased in gra(k) comparing to those in the wild-type Kitaake.Genetic analysis showed that the gra phenotype was controlled by a single recessive nucleic gene. By using 5,168 recessive F2individuals derived from the cross of gra(k) 9 Jodan, the locus of the gene Gra(k) was delimited in a DNA region of 200 kb between the makers B-31 and P11 on chromosome 5. Sequencing analysis indicated thatthe three functionally annotated genes, LOC_Os05g23700,LOC_Os05g23720, and LOC_Os05g23740, were all deleted in the 200 kb region in the mutant gra(k). Transgenic test revealed that the gra(k) plants over-expressing LOC_Os05g23740CDS were restored to normal green as the wild-type Kitaake. Our results proved that the deletion of the Dna K protein gene LOC_Os05g23740(encoding the chaperon protein Os Hsp70CP1) led to the gra phenotype in the mutant gra(k).

Characterization and Fine Mapping of a Novel Vegetative Senescence Lethal Mutant Locus in Rice

Mutants showing spontaneous cell death in the absence of pathogen attack are called lesion mimic mutants （lmm） （Lorrain et al., 2003）. These mutants usually exhibit typical hypersensitive responses （HRs） within or around the lesion spots, which are frequently observed in plants challenged with avirulent pathogens （Lorrain et al., 2003）. A number of these mutants have been characterized in rice （Zeng et al., 2004）, Arabidopsis （Guo et al., 2013）, maize （Wang et al., 2013） and barley （Persson et al., 2008）. Most lmm show enhanced resistance to various pathogens （Huang et al., 2011）, because HR is usually accompanied with enhanced defense responses, such as reactive oxygen species （ROS） activation （Qiao et al., 2010） and increased expression of pathogenesis-related genes （Lorrain et al., 2003）. Additionally, most lmm exhibit defects in growth and development due to the disordered physiolog- ical and molecular processes caused by the lesion spots. Thus, lmm are powerful tools for the study of the molecular mech- anisms of cell death, plant development and disease resistance （Lorrain et al., 2003; Babu et al., 2011）.