Changes in human lifestyle and food consumption have resulted in a large increase in the incidence of type-2 diabetes, obesity, and colon disease, especially in Asia. These conditions are a growing threat to human health, but consumption of foods high in resistant starch (RS) can potentially reduce their incidence. Strategies to increase RS in rice are limited by a lack of knowledge of its molecular basis. Through map-based cloning of a RS locus in indica rice, we have identified a defective soluble starch synthase gene (SSIIIa) responsible for RS production and further showed that RS production is dependent on the high expression of the Waxy a (Wx a ) allele, which is prevalent in indica varieties. The resulting RS has modified granule structure; high amylose, lipid, and amylose-lipid complex; and altered physicochemical properties. This discovery provides an opportunity to increase RS content of cooked rice, especially in the indica varieties, which predominates in southern Asia.diabetes | resistant starch biosynthesis | soluble starch synthase | granule-bound starch synthase | amylose-lipid complex I ncreases in the incidence of type-2 diabetes are being observed throughout the world. This increase is thought to be due to changes in both diet and lifestyle (1, 2) and is increasingly apparent in Asia. Consumption of foods high in resistant starch (RS) can help to control type-2 diabetes, because its slow digestion and absorption by the small intestine decreases postprandial glucose and insulin responses (3). Foods high in RS also potentially protect against pathogen infection, diarrhea, inflammatory bowel disease, colon cancer, and chronic renal and hepatic diseases. Consumption of RS can increase satiety and reduce calorie intake to help weight management (3). Thus, improvement of the amounts and properties of RS in foods is an important goal.Rice (Oryza sativa L.) is consumed by more than half the world's population (4), and for many, it is the primary source of nutrients and carbohydrates for energy. Consumption of 18-20 g of RS (5, 6) is recommended per day for health benefits, but hot cooked rice typically contains <3% RS (7). Rice varieties or mutants with improved RS have been identified, such as Goami No. 2, Gongmi No. 3, RS111, and Jiangtangdao 1 (7-10).A high-RS, high-amylose transgenic rice line has been developed by suppressing the expression of starch branching enzymes (SBEs) (11) and a mutation of SBEIIb cosegregated with RS content in rice (8). In other cereals, down-regulation of soluble starch synthase (SS) SSIIa and of SBE results in greater RS in barley (12, 13) and wheat (14)(15)(16)(17)(18)(19)(20). Because the molecular basis underlying RS production is largely unknown, discovery of new RS genes is vital both for the elucidation of RS biosynthesis and for the breeding of high-RS varieties. We therefore screened a mutagenized population of the hybrid-rice restorer line R7954 for mutants with high RS in hot cooked rice. This strategy was designed to identify new RS genes of practical value ...

A metabolite profiling approach based on gas chromatography-mass spectrometry (GC-MS) was used to investigate time-dependent metabolic changes in the course of the germination of rice. Brown rice kernels were soaked and incubated for a total of 96 h under ambient conditions. Samples taken during the germination process were subjected to an extraction and fractionation procedure covering a broad spectrum of lipophilic (e.g., fatty acid methyl esters, hydrocarbons, fatty alcohols, sterols) and hydrophilic (e.g., sugars, acids, amino acids, amines) low molecular weight rice constituents. Investigation of the obtained fractions by GC resulted in the detection of 615 distinct peaks, of which 174 were identified by means of MS. Statistical assessment of the data via principal component analysis demonstrated that the metabolic changes during the germination process are reflected by time-dependent shifts of the scores, which were similar for the three rice materials investigated. Analysis of the corresponding loadings showed that polar metabolites were major contributors to the separation along the first principal component. Relative quantifications based on standardized peak heights revealed dynamic changes of the metabolites in the course of the germination.

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 .

These authors contributed equally to this work. SUMMARYEmerging evidence indicates a close connection between cell-cycle progression and the plant immune responses. In Arabidopsis, MODIFIER OF snc1-1 (MOS1) modulates a number of processes including endoreduplication and plant disease resistance, but the molecular mechanism underlying this modulation was not fully understood. Here, we provide biochemical and genetic evidence that TEOSINTE BRANCHED 1, CYCLOIDEA, PCF1 (TCP) transcription factors TCP15 and its homologues are mediators of MOS1 function in the immune response and are likely to be also involved in cell-cycle control. MOS1 and TCP proteins have a direct physical interaction. They both bind to the promoter of the immune receptor gene SUPRESSOR OF npr1-1, CONSTITUTIVE 1 (SNC1) and modulate its expression and consequently immune responses. MOS1 and TCP15 both affect the expression of cell-cycle genes D-type CYCLIN 3;1 (CYCD3;1), which may mediate the MOS1 function in cell-cycle modulation. In addition, CYCD3;1 overexpression upregulates immune responses, and SNC1 expression. This study investigated and revealed a role for MOS1 in transcriptional regulation through TCP15 and its homologues. This finding suggests the coordination of cell-cycle progression and plant immune responses at multiple levels.

The hydrolysis of starch is a key factor for controlling the glycemic index (GI). Slow digestion properties of starch lead to slower glucose release and lower glycemic response. Food with high resistant starch (RS) possesses great value for controlling the GI. To elucidate the factors that play a role in slow digestibility, seven rice mutants different in RS contents were selected for comparative studies. The degree of hydrolysis showed highly significant correlation with RS, apparent amylose content (AAC), lipid content (LC), and other starch physiochemical properties in all these materials with different RS contents. The rate of in vitro digestible starch correlated positively with RS, whereas digestibility was affected mostly by lipid content for those mutants with similar RS. Starch-lipid complexes and short chains with degrees of polymerization (DP) of 8-12 strongly influenced starch digestion. The integrity of aggregated starch and the number of round starch granules might influence the digestibility of starch directly.

Amylopectin is the principle component of starch. To elucidate the relationships between amylopectin and resistant starch content, six rice mutants with altered fine structure of amylopectin were selected for comparative studies with the primary wild type and two types of amylose‐extender (ae) mutants. Significant differences in resistant starch content were observed among mutants with similarity or differences in amylose levels. Mutants high in resistant starch had significantly increased proportions of short amylopectin chains with DP≤12, decreased levels of intermediate chains with size of 13≤DP≤36, and decreased fractions of long chains with DP≥37. Additionally, there was a mutant different to ae, which was characterized by an increased level of short chains with 8≤DP≤12 and 13≤DP≤24, and a decreased proportion of long chains with DP≥37. The increased contents of short chains with 8≤DP≤12 and decreased of intermediate and long chains with 24≤DP were clearly associated with the increase of resistant starch in rice.

BackgroundThe effector AvrPiz-t of Magnaporthe oryzae has virulence function in rice. However, the mechanism underlying its virulence in host is not fully understood.ResultsIn this study, we analyzed the function of AvrPiz-t interacting protein 12 (APIP12) in rice immunity. APIP12 significantly bound to AvrPiz-t and APIP6 in its middle portion and N-terminus, respectively, in yeast two-hybrid assay. Glutathione S-transferase (GST) pull-down assay further verified the interactions of APIP12 with AvrPiz-t and APIP6. APIP12 encodes a homologue of nucleoporin protein Nup98 without the conserved domain of Phe-Gly repeats and has no orthologue in other plants. Both knockout and knockdown of APIP12 caused enhanced susceptibility of rice plants to virulent isolates of M. oryzae. The expression of some pathogenesis-related (PR) genes was reduced in both knockout and knockdown mutants, suggesting that APIP12 is required for the accumulation of transcripts of PR genes upon the infection. It is worth noting that neither knockout/knockdown nor overexpression of APIP12 attenuates Piz-t resistance.ConclusionsTaken together, our results demonstrate that APIP12 is a virulence target of AvrPiz-t and is involved in the basal resistance against M. oryzae in rice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-017-0144-7) contains supplementary material, which is available to authorized users.

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