The regulatory role of CARBON STARVED ANTHER-mediated photoperiod-dependent male fertility in rice.

Environmental signals, especially daylength, play important roles in determining fertility in photoperiod-sensitive genic male sterile (PGMS) lines that are critical to sustain production of high-yielding hybrid rice (Oryza sativa) varieties. However, the mechanisms by which PGMS lines perceive changes in photoperiod and transmit those signals to elicit downstream effects are not well understood. In this study, we compared the transcriptomes from the leaves and anthers of carbon starved anther (csa), a PGMS line, to wild-type (WT) tissues under different photoperiods. Components of circadian clock in the leaves, including Circadian Clock-Associated 1 and Pseudo-Response Regulator (PRR95), played vital roles in sensing the photoperiod signals. Photoperiod signals were weakly transduced to anthers, where gene expression was mainly controlled by the CSA allele. CSA played a critical role in regulating sugar metabolism and cell wall synthesis in anthers under short-day conditions, and transcription of key genes inducing csa-directed sterility was upregulated under long-day (LD) conditions though not to WT levels, revealing a mechanism to explain the partial restoration of fertility in rice under LD conditions. Eight direct targets of CSA regulation were identified, all of which were genes involved in sugar metabolism and transport (cell wall invertases, SWEETs, and monosaccharide transporters) expressed only in reproductive tissues. Several hub genes coordinating the effects of CSA regulation were identified as critical elements determining WT male fertility and further analysis of these and related genes will reveal insights into how CSA coordinates sugar metabolism, cell wall biosynthesis, and photoperiod sensing in rice anther development.

Transcriptome Analysis Reveals Photoperiod-Associated Genes Expressed in Rice Anthers.

Environmental conditions, such as photoperiod and temperature, can affect male fertility in plants. While this feature is heavily exploited in rice to generate male-sterile lines for hybrid breeding, the underlying molecular mechanisms remain largely unknown. In this study, we use a transcriptomics approach to identify key genes and regulatory networks affecting pollen maturation in rice anthers in response to different day lengths. A total of 11,726 differentially expressed genes (DEGs) were revealed, of which 177 were differentially expressed at six time points over a 24-h period. GO enrichment analysis revealed that genes at all time points were enriched in transport, carbohydrate, and lipid metabolic processes, and signaling pathways, particularly phytohormone signaling. In addition, co-expression network analysis revealed four modules strongly correlated with photoperiod. Within these four modules, 496 hub genes were identified with a high degree of connectivity to other photoperiod-sensitive DEGs, including two previously reported photoperiod- and temperature-sensitive genes affecting male fertility, Carbon Starved Anther and UDP-glucose pyrophosphorylase, respectively. This work provides a new understanding on photoperiod-sensitive pollen development in rice, and our gene expression data will provide a new, comprehensive resource to identify new environmentally sensitive genes regulating male fertility for use in crop improvement.

The pathophysiological mechanism of ischemic stroke after hypobaric hypoxia simulation at high altitude.

Tibet is an area in China with a high incidence of stroke, typically attributed to hypobaric hypoxia. The present study aimed to observe the neuronal injury of ischemic stroke after hypobaric hypoxia and explore the mechanism by which N-methyl-D-aspartate receptor (NMDAR) and its downstream pathways are involved. This study employed a hypobaric chamber to imitate high altitude at 4000 m. After hypoxia, the middle cerebral artery occlusion (MCAO) model was used to mimic ischemic stroke. Behavioral tests and measurements of infarct area were used to observe neuronal injuries. The expression of NMDAR, Ca2+/calmodulin-dependent protein kinase II (CaMKII) and phosphorylated CaMKII (Threonine 286) (P-CaMKII) was tested by western blot, and hematological tests were used to count the number of red blood cells (RBCs) and hemoglobin. Compared with the plain+MCAO group, the neurological deficit scores and infarct area of rats in the 4000 m + MCAO group were all decreased, and the protein expression of NMDAR, CaMKII and P-CaMKII was reduced. Compared with the plain group, the numbers of RBCs, hemoglobin and hematocrit were increased in the 4000 m group; compared with the 4000 m groups, the three indexes were increased in the 4000 m + MCAO groups. The neuronal injuries after hypoxia were not more serious than those in rats enduring ischemia and reperfusion in plain. The underlying mechanisms were related to the decreased expression of NMDAR and CaMKII; furthermore, the increased numbers of RBCs and hemoglobin may be crucial mechanisms for the incidence and development of ischemic stroke at high altitude.