Purine permease (PUP) family gene PUP11 positively regulates the rice seed setting rate by influencing seed development

KEY MESSAGE

Purine permease PUP11 is essential for rice seed development, regulates the seed setting rate, and influences the cytokinin content, sugar transport, and starch biosynthesis during grain development. The distribution of cytokinins in plant tissues determines plant growth and development and is regulated by several cytokinin transporters, including purine permease (PUP). Thirteen PUP genes have been identified within the rice genome; however, the functions of most of these genes remain poorly understood. We found that pup11 mutants showed extremely low seed setting rates and a unique filled seed distribution. Moreover, seed formation arrest in these mutants was associated with the disappearance of accumulated starch 10 days after flowering. PUP11 has two major transcripts with different expression patterns and subcellular locations, and further studies revealed that they have redundant positive roles in regulating the seed setting rate. We also found that type-A Response Regulator (RR) genes were upregulated in the developing grains of the pup11 mutant compared with those in the wild type. The results also showed that PUP11 altered the expression of several sucrose transporters and significantly upregulated certain starch biosynthesis genes. In summary, our results indicate that PUP11 influences the rice seed setting rate by regulating sucrose transport and starch accumulation during grain filling. This research provides new insights into the relationship between cytokinins and seed development, which may help improve cereal yield.

OsMFT1 Inhibits Seed Germination by Modulating Abscisic Acid Signaling and Gibberellin Biosynthesis under Salt Stress in Rice

Seed dormancy and germination are regulated by endogenous gene expression as well as hormonal and environmental conditions, such as salinity, which greatly inhibits seed germination. MOTHER OF FT AND TFL1 (MFT), which encodes a phosphatidylethanolamine-binding protein, is a key regulator of seed germination in Arabidopsis thaliana. There are two orthologous genes of AtMFT in rice (Oryza sativa), namely, OsMFT1 and OsMFT2. However, the functions of these two genes in regulating rice seed germination under salt stress remain unknown. In this study, we found that seeds of loss-of-function osmft1 mutants germinated faster than wild-type (WT) seeds under salt stress, but this was not the case for loss-of-function osmft2 mutants. Overexpression of OsMFT1 (OsMFT1OE) or OsMFT2 increased the sensitivity to salt stress during seed germination. Transcriptome comparisons of osmft1 vs WT in the absence and presence of salt stress yielded several differentially expressed genes, which were associated with salt stress, plant hormone metabolism and signaling pathways, such as B-BOX ZINC FINGER 6, O. sativa bZIP PROTEIN 8 and GIBBERELLIN (GA) 20-oxidase 1. In addition, the sensitivity of OsMFT1OE seeds to GA and osmft1 seeds to abscisic acid (ABA) during seed germination increased under salt stress. Overall, our results indicate that ABA and GA metabolism and their signaling pathways are regulated by OsMFT1, modulating seed germination in rice under salt stress.

Cytokinin oxidase/dehydrogenase family genes exhibit functional divergence and overlap in rice growth and development, especially in control of tillering

Cytokinins play key roles in plant growth and development, and hence their biosynthesis and degradation have been extensively studied. Cytokinin oxidase/dehydrogenases (CKXs) are a group of enzymes that regulate oxidative cleavage to maintain cytokinin homeostasis. In rice, 11 CKX genes have been identified to date; however, most of their functions remain unknown. In this study, we comprehensively examined the expression patterns and functions of the CKXs in rice by using CRISPR/Cas9 technology to construct mutants of all 11 genes. The results revealed that the ckx single-mutants and higher-order ckx4 ckx9 mutant lines showed functional overlaps and sub-functionalization. Notably, the ckx1 ckx2 and ckx4 ckx9 double-mutants displayed contrasting phenotypic changes in tiller number and panicle size compared to the wild-type. In addition, we identified several genes with significantly altered expression in both the ckx4 and ckx9 single-mutant and double-mutant plants. Many of the differentially expressed genes were found to be associated with auxin and cytokinin pathways, and cytokinins in the ckx4 ckx9 double-mutant were increased compared to the wild-type. Taken together, our findings provide new insights into the functions of CKX genes in rice growth and may provide the foundations for future studies aimed at improving rice yield.

SWI2/SNF2 chromatin remodeling ATPases SPLAYED and BRAHMA control embryo development in rice

Chromatin remodeling ATPases OsSYD and OsBRM are involved in shoot establishment, and both affect OSH gene transcription. OsSYD protein interacts with RFL, but OsBRM does not. In plants, SPLAYED (SYD) and BRAHMA (BRM) encode chromatin remodeling ATPases that use the energy derived from ATP hydrolysis to restructure nucleosomes and render certain genomic regions available to transcription factors. However, the function of SYD and BRM on rice growth and development is unknown. Here, we constructed ossyd and osbrm mutants using CRISPR/Cas9 technology and analyzed the effects of mutations on rice embryo development. We discovered that the ossyd and osbrm mutants exhibited severe defects during embryonic development, whereas endosperm development was normal. These results indicated that the development of the embryo and endosperm is independent of each other. Consequently, the ossyd- and osbrm-null mutants did not germinate due to the abnormal embryos. Furthermore, we observed the embryos of ossyd- and osbrm-null mutants, and they indeed had distinct differentiation defects in shoot establishment, acquired during embryogenesis. To verify the function of OsSYD and OsBRM in embryogenesis, we measured the transcript levels of marker genes at different stages. Compared with wild type, the expression levels of multiple OSH genes were significantly reduced in the mutants, which was consistent with the defective shoot establishment phenotypes. The interaction between SYD and RICE FLORICAULA/LFY (RFL) was revealed using a yeast two-hybrid screening system, suggesting that the interaction between the LFY homolog and chromatin remodeling ATPases is ubiquitous in plants. Collectively, our findings provide the basis for elucidating the function of OsSYD and OsBRM during embryo development in rice.

DNA methylation profiles in placenta and its association with gestational diabetes mellitus

Emerging evidences indicate that placenta plays a critical role in gestational diabetes mellitus (GDM). DNA methylation could be associated with altered placental development and functions. This study is to uncover the genome-wide DNA methylation patterns in this disorder. DNA methylation was measured at >385,000 CpG sites using methylated DNA immunoprecipitation (MeDIP) and a huamn CpG island plus promoter microarray. We totally identified 6,641 differentially methylated regions (DMRs) targeting 3,320 genes, of which 2,729 DMRs targeting 1,399 genes, showed significant hypermethylation in GDM relative to the controls, whereas 3,912 DMRs targeting 1,970 genes showed significant hypomethylation. Functional analysis divided these genes into different functional networks, which mainly involved in the pathways of cell growth and death regulation, immune and inflammatory response and nervous system development. In addition, the methylation profiles and expressions of 4 loci (RBP4, GLUT3, Resistin and PPARα) were validated by BSP for their higher log2 ratio and potential functions with energy metabolism. This study demonstrates aberrant patterns of DNA methylation in GDM which may be involved in the pathophysiology of GDM and reflect the fetal development. Future work will assess the potential prognostic and therapeutic value for these findings in GDM.

Association of maternal KIR and fetal HLA-C genes with the risk of preeclampsia in the Chinese Han population

INTRODUCTION

This study is to investigate the distribution of inhibitory and activating killer-cell immunoglobulin-like receptors (KIRs) and the combination of KIR/human leukocyte antigen (HLA)-C in women with preeclampsia in the Chinese Han population.

METHODS

A total of 271 patients and 295 controls were enrolled in our study. The inhibitory/activating KIR and HLA-C genes were detected using the PCR-SSP (polymerase chain reaction with sequence-specific primers) method.

RESULTS

Our result showed that decreased numbers of individual activating KIR genes (2DS2, 2DS3, and 2DS5) were observed in women with preeclampsia. Furthermore, the gene frequency of total activating KIRs was significantly lower in patients compared with that of the controls (P = 0.03). The frequency of the KIR2DL1 gene was increased in women with preeclampsia when a homozygous HLA-C2 allele appeared in the fetus.

CONCLUSION

The results suggest that a KIR genetic variation might influence the risk of preeclampsia. The lack of activating KIRs could possibly lower uterine natural killer (uNK) cell activation, thereby contributing to the pathogenesis of preeclampsia. Moreover, the imbalance of the inhibitory or activating signals at the maternal-fetal interface seems to play a regulatory role in the occurrence of preeclampsia.

Influence of colorectal laparoscopic surgery on dissemination and seeding of tumor cells

BACKGROUND

This study aimed to compare the influence of colorectal laparoscopic surgery and conventional surgery on dissemination and seeding of tumor cells.

METHODS

Intraoperative peritoneal lavage cytology was performed for 36 patients with colorectal cancer during colorectal laparoscopic surgery and for 45 patients with colorectal cancer during conventional surgery. Cytology was examined twice: immediately after opening of the peritoneal cavity and just before closure of the abdomen. Saline was poured into the peritoneal cavity, and 100 ml fluid was retrieved after irrigation. Laparoscopic instruments were lavaged after surgery with 100 ml of saline. Carbon dioxide (CO(2)) was derived through the trocar side orifice after pneumoperitoneum during laparoscopic coloectomy and filtered through 100 ml of saline. Cytologic examination of the filtrate was performed after the filtration process, smear, cell block, and staining.

RESULTS

Malignant cells were not detected in the CO(2) filtrate gas. The incidence of positive cytology in the lavage of the instruments during laparoscopic surgery was 2.78%. The incidence of positive cytology during laparoscopic surgery was 33.33% in the prelavage and 8.33% in the postlavage. The incidence of positive cytology during conventional surgery was 33.33% in the prelavage and 11.11% in the postlavage.

CONCLUSION

During colorectal laparoscopic surgery, CO(2) pneumoperitoneum does not affect tumor cell dissemination and seeding. In this study, laparoscopic techniques used in colorectal cancer surgery were not associated with a greater risk for intraperitoneal dissemination of cancer cells than the conventional technique.