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Abstract: Many rice breeding programs have currently reached yield plateaus as a result of limited genetic variability in parental strains. Dongxiang common wild rice (Oryza rufipogon Griff.) is the progenitor of cultivated rice (Oryza sativa L.) and serves as an important gene pool for the genetic improvement of rice cultivars. In this study, heterotic loci (HLs) associated with six yield-related traits were identified in wild and cultivated rice and investigated using a set of 265 introgression lines (ILs) of O. rufipogon Griff. in the background of the Indica high-yielding cultivar Guichao 2 (O. sativa L.). Forty-two HLs were detected by a single point analysis of mid-parent heterosis values from test cross F1 offspring, and 30 (71.5%) of these HLs showed significantly positive effects, consistent with the superiority shown by the F1 test cross population in the six yield-related traits under study. Genetic mapping of hsp11, a locus responsible for the number of spikelets per panicle, confirmed the utility of these HLs. The results indicate that favorable HLs capable of improving agronomic traits are available. The identification of HLs between wild rice and cultivated rice could lead to a new strategy for the application of heterosis in rice breeding. [Copyright &y& Elsevier]

Abstract: Programmed cell death (PCD) is a crucial process for plants during development and environmental stress. OsPDCD5, is an ortholog to mammalian programmed cell death 5 gene. Here we report that decreased expression of OsPDCD5 caused by antisense technology could induce pollen sterility in photoperiod-sensitive rice. The male sterility of transgenic plants is reversible, determined mainly by photoperiod. Transgenic plants are sterile under long-day photoperiod (≥13.5h sunlight) with postponed heading time, while they can restore fertility under short-day photoperiod (below 13h sunlight). Analysis of tissue sections of anthers displays the tapetum cells of the anther wall retard PCD process in transgenic plants under long-day photoperiod. The retarded PCD was also confirmed by DNA fragmentation. In F1 hybrids made from transgenic plants with antisense-OsPDCD5 and japonica rice varieties, lower transcript inhibition could restore fertility, under certain photoperiod and temperatures. The surprising discovery of the photosensitive male fertility suggested that by using specific photoperiods, the male sterility (PGMS) could be used for commercial production of hybrid rice using a two-line breeding system. The transgenic hybrid strategy was easy to apply, reduced costs and shortened the breeding period. It provides great advantages for commercial applications in rice and other crops. [Copyright &y& Elsevier]

Abstract: Programmed cell death (PCD) is crucial for plants during development and stress survival. OsPDCD5, an ortholog to mammalian-programmed cell death 5, was previously cloned from rice (Oryza sativa, cv Zhenxian 97A), and its overexpression can induce PCD in transgenic rice. In the present study, immunoblotting analysis revealed that the OsPDCD5 protein was widely expressed in the tassel, leaf, leaf sheath, and different parts of the stem but not in the anther. RT-PCR analysis showed that OsPDCD5 was related to the senescence of leaf and root tissues as well as the development of stem tissues. Furthermore, OsPDCD5 was up-regulated by UV-B irradiation. Calcineurin B-like interacting protein kinase 23 (OsCIPK23), which is involved in the calcineurin B-like proteins (CLBs)/CBL-interacting protein kinases (CIPKs) signaling network, was identified as interacting with OsPDCD5 by yeast two-hybrid screening and subsequently confirmed by pull-down assay in vitro. Present findings may shed light on the investigation of the biochemical function of OsPDCD5 in rice. [Copyright &y& Elsevier]