Disruption of a Rice Pentatricopeptide Repeat Protein Causes a Seedling-Specific Albino Phenotype and Its Utilization to Enhance Seed Purity in Hybrid Rice Production    

Abstract

The pentatricopeptide repeat (PPR) gene family represents one of the largest gene families in higher plants. Accumulating data suggest that PPR proteins play a central and broad role in modulating the expression of organellar genes in plants. Here we report a rice (Oryza sativa) mutant named young seedling albino (ysa) derived from the rice thermo/photoperiod-sensitive genic male-sterile line Pei'ai64S, which is a leading male-sterile line for commercial two-line hybrid rice production. The ysa mutant develops albino leaves before the three-leaf stage, but the mutant gradually turns green and recovers to normal green at the sixleaf stage. Further investigation showed that the change in leaf color in ysa mutant is associated with changes in chlorophyll content and chloroplast development. Map-based cloning revealed that YSA encodes a PPR protein with 16 tandem PPR motifs. YSA is highly expressed in young leaves and stems, and its expression level is regulated by light. We showed that the ysa mutation has no apparent negative effects on several important agronomic traits, such as fertility, stigma extrusion rate, selfed seed-setting rate, hybrid seed-setting rate, and yield heterosis under normal growth conditions. We further demonstrated that ysa can be used as an early marker for efficient identification and elimination of false hybrids in commercial hybrid rice production, resulting in yield increases by up to approximately 537 kg ha 21 .

A Rice Virescent-Yellow Leaf Mutant Reveals New Insights into the Role and Assembly of Plastid Caseinolytic Protease in Higher Plants

“…For example, the rice young seedling albino (ysa) mutant develops albino leaves before the third leaf stage with decreased chlorophyll synthesis and delayed chloroplast development, but the mutant recovers to normal green by the sixth leaf stage. YSA encodes a pentatricopeptide repeat protein with 16 tandem pentatricopeptide repeat motifs, which likely plays a central role in organellar RNA metabolism (Su et al, 2012). These studies together convincingly demonstrate that chloroplast biogenesis and leaf development are under highly sophisticated genetic control at multiple levels, including DNA synthesis, gene expression, RNA processing, and protein synthesis and degradation.…”

Albino Leaf 1 that Encodes the Sole Octotricopeptide Repeat Protein Is Responsible for Chloroplast Development in Rice

“…So far, most of the helical repeat proteins mentioned above were identified from Arabidopsis and green algae. Only a few of them were isolated from rice (Oryza sativa), such as YSA, ECB2-1, and OsV4 (Cao et al, 2011;Su et al, 2012;Gong et al, 2014). To our knowledge, the role of RAP in chloroplast development is still unknown in rice.…”

“…PPR proteins in chloroplast have been implicated as being involved in regulating RNA splicing (Schmitz-Linneweber et al, 2006;de Longevialle et al, 2007;Ichinose et al, 2012), RNA editing (Kotera et al, 2005;Okuda et al, 2007;Chateigner-Boutin et al, 2008;Cai et al, 2009;Yu et al, 2009;Zhou et al, 2009;Tseng et al, 2010;Sosso et al, 2012), RNA cleavage (Meierhoff et al, 2003;Hattori et al, 2007), and translation (Williams and Barkan, 2003;Tavares-Carreón et al, 2008) during plant development. The disruption of tetratricopeptide repeat or PPR proteins generally causes defects in the development of chloroplast, eventually leading to the albino or chlorotic leaf phenotype in plants (Chi et al, 2008(Chi et al, , 2010Cao et al, 2011;Su et al, 2012;Gong et al, 2014).…”

RNase ZS1 processes UbL40 mRNAs and controls thermosensitive genic male sterility in rice

“…H ybrid rice, which yields B10-20% more grain than conventional rice, has been planted in B60% (B17 million hectares) of the rice-growing area in China and is also cultivated in many other countries, thus providing a key component of the global food supply [1][2][3] . Rice is strictly selfpollinating; therefore, hybrid varieties are bred using male-sterile maternal lines that fail to produce viable pollen, thus preventing self-pollination.…”