Identification and Gene Mapping of anearly senescence leaf 4Mutant of Rice

Abstract

2713ReseaRch T he leaf is the primary site of photosynthesis and respiration in plants. The shape and lifespan of the leaf is strongly associated with crop yield (Yan et al., 2008). Early senescence often causes significant losses in crop yield and quality. For example, delay of leaf senescence by only 1 d theoretically increases rice grain yield by 2%, with an approximately 1% increase in grain yield observed in practice (Duan et al., 1997). Therefore, studying premature senescence genes in rice is crucial not only for molecular breeding of rice, but also for comparing the mechanisms responsible for leaf senescence in monocotyledonous and dicotyledonous plants. Leaf senescence is a complex physiological event that constitutes the last stage of leaf development and aBSTRaCT An early senescence leaf 4 (esl4) mutant of rice (Oryza sativa L.) displayed yellowing followed by severe chlorosis of the leaf apex and margin from the late jointing stage to maturity. The content of photosynthetic pigments in the mutant was significantly lower than in wild-type plants, and abnormalities in cell structure were detected in the mutant leaf blade. Stomatal conductance and rates of photosynthesis and transpiration were lower in esl4 than in wild-type plants. Furthermore, compared with the wild-type, the activities of superoxide dismutase and catalase were significantly lower in esl4, whereas peroxidase activity was significantly higher in esl4. Genetic analysis indicated that the early senescence of esl4 was controlled by a recessive nuclear gene. A population of 879 F 2 mutants was used to fine-map the ESL4 gene to chromosome 4 between the insertion and deletion primers S4-42 and S4-67. This 63-kb stretch encodes 12 uncharacterized open reading frames. Quantitative real-time polymerase chain reaction analysis (qrT-pCr) revealed that levels of SGR transcripts were considerably more abundant in esl4 than in wild-type. These results provide a foundation for map-based cloning and functional analysis of the ESL4 gene.

Identification and Gene Mapping of an Early Senescent Leaf Mutant esl11 of Rice

“…Early leaf senescence genes have been reported in different chromosomes. Two genes, Esl2 and Esl4, were located on chromosome 4 (Xu et al, 2012;Guo et al, 2014), one in chromosome 3 (Esl5; Sang et al, 2014) and one in chromosome 7 (Esl10; Chen et al, 2018). The esl11 gene in this study was also found in chromosome 7 but was located far from Esl10, in a different interval.…”

“…Two genes, Esl2 and Esl4, were located on chromosome 4 (Xu et al, 2012;Guo et al, 2014), one in chromosome 3 (Esl5; Sang et al, 2014) and one in chromosome 7 (Esl10; Chen et al, 2018). Two genes, Esl2 and Esl4, were located on chromosome 4 (Xu et al, 2012;Guo et al, 2014), one in chromosome 3 (Esl5; Sang et al, 2014) and one in chromosome 7 (Esl10; Chen et al, 2018).…”

“…Esl2 starts from the booting stage and the edges and tips of the leaves become yellowing and senescent (Xu et al, 2012). Esl4 had the same yellowing on edges and tips of the leaves with yellowing and senescent, but it starts from the jointing stage (Guo et al, 2014). The Sms1 mutant has the early senescence phenotype from the three-leaf stage, and leaves appear long striped with lesion spots (Yan et al, 2010).…”

“…These included psl1 (Wang et al, 2006), pgl2 (Zhu et al, 2007), psl3 (Fang et al, 2010), esl2 (Xu et al, 2012), lad (Du et al, 2012), esl3 (Miao et al, 2013), esl4 (Guo et al, 2014), esl5 , esl6 (Yang et al, 2016a), esl9 (Xiao et al, 2017), and esl10 (Chen et al, 2018). These included psl1 (Wang et al, 2006), pgl2 (Zhu et al, 2007), psl3 (Fang et al, 2010), esl2 (Xu et al, 2012), lad (Du et al, 2012), esl3 (Miao et al, 2013), esl4 (Guo et al, 2014), esl5 , esl6 (Yang et al, 2016a), esl9 (Xiao et al, 2017), and esl10 (Chen et al, 2018).…”

“…Numerous early leaf senescence mutants of rice have been identified, and their molecular positioning has been reported. These included psl1 (Wang et al, 2006), pgl2 (Zhu et al, 2007), psl3 (Fang et al, 2010), esl2 (Xu et al, 2012), lad (Du et al, 2012), esl3 (Miao et al, 2013), esl4 (Guo et al, 2014), esl5 , esl6 (Yang et al, 2016a), esl9 (Xiao et al, 2017), and esl10 (Chen et al, 2018). However, few senescence-associated genes have been cloned in rice, such as NYC4 (Yamatani et al, 2013), OsNAP (Liang and Chu, 2015), NOE1 (Lin et al, 2012), and LTN1 (Hu et al, 2011).…”