Chloroplast development is an important determinant of plant productivity and is controlled by environmental factors including amounts of light and nitrogen as well as internal phytohormones including cytokinins and gibberellins (GA). The paralog GATA transcription factors GNC and CGA1/GNL up-regulated by light, nitrogen and cytokinin while also being repressed by GA signaling. Modifying the expression of these genes has previously been shown to influence chlorophyll content in Arabidopsis while also altering aspects of germination, elongation growth and flowering time. In this work, we also use transgenic lines to demonstrate that GNC and CGA1 exhibit a partially redundant control over chlorophyll biosynthesis. We provide novel evidence that GNC and CGA1 influence both chloroplast number and leaf starch in proportion to their transcript level. GNC and CGA1 were found to modify the expression of chloroplast localized GLUTAMATE SYNTHASE (GLU1/Fd-GOGAT), which is the primary factor controlling nitrogen assimilation in green tissue. Altering GNC and CGA1 expression was also found to modulate the expression of important chlorophyll biosynthesis genes (GUN4, HEMA1, PORB, and PORC). As previously demonstrated, the CGA1 transgenic plants demonstrated significantly altered timing to a number of developmental events including germination, leaf production, flowering time and senescence. In contrast, the GNC transgenic lines we analyzed maintain relatively normal growth phenotypes outside of differences in chloroplast development. Despite some evidence for partial divergence, results indicate that regulation of both GNC and CGA1 by light, nitrogen, cytokinin, and GA acts to modulate nitrogen assimilation, chloroplast development and starch production. Understanding the mechanisms controlling these processes is important for agricultural biotechnology.

The interaction between phytohormones is an important mechanism which controls growth and developmental processes in plants. Deciphering these interactions is a crucial step in helping to develop crops with enhanced yield and resistance to environmental stresses. Controlling the expression level of OsAP2-39 which includes an APETALA 2 (AP2) domain leads to phenotypic changes in rice. Overexpression of OsAP2-39 leads to a reduction in yield by decreasing the biomass and the number of seeds in the transgenic rice lines. Global transcriptome analysis of the OsAP2-39 overexpression transgenic rice revealed the upregulation of a key Abscisic Acid (ABA) biosynthetic gene OsNCED-I which codes for 9-cis-epoxycarotenoid dioxygenase and leads to an increase in the endogenous ABA level. In addition to OsNCED-1, the gene expression analysis revealed the upregulation of a gene that codes for the Elongation of Upper most Internode (EUI) protein, an enzyme that catalyzes 16α, 17-epoxidation of non-13-hydroxylated GAs, which has been shown to deactivate gibberellins (GAs) in rice. The exogenous application of GA restores the wild-type phenotype in the transgenic line and ABA application induces the expression of EUI and suppresses the expression of OsAP2-39 in the wild-type line. These observations clarify the antagonistic relationship between ABA and GA and illustrate a mechanism that leads to homeostasis of these hormones. In vivo and in vitro analysis showed that the expression of both OsNCED-1 and EUI are directly controlled by OsAP2-39. Together, these results reveal a novel mechanism for the control of the ABA/GA balance in rice which is regulated by OsAP2-39 that in turn regulates plant growth and seed production.

The major source of nitrogen for rice (Oryza sativa L.) is ammonium (NH4 +). The NH4 + uptake of roots is mainly governed by membrane transporters, with OsAMT1;1 being a prominent member of the OsAMT1 gene family that is known to be involved in NH4 + transport in rice plants. However, little is known about its involvement in NH4 + uptake in rice roots and subsequent effects on NH4 + assimilation. This study shows that OsAMT1;1 is a constitutively expressed, nitrogen-responsive gene, and its protein product is localized in the plasma membrane. Its expression level is under the control of circadian rhythm. Transgenic rice lines (L-2 and L-3) overexpressing the OsAMT1;1 gene had the same root structure as the wild type (WT). However, they had 2-fold greater NH4 + permeability than the WT, whereas OsAMT1;1 gene expression was 20-fold higher than in the WT. Analogous to the expression, transgenic lines had a higher NH4 + content in the shoots and roots than the WT. Direct NH4 + fluxes in the xylem showed that the transgenic lines had significantly greater uptake rates than the WT. Higher NH4 + contents also promoted higher expression levels of genes in the nitrogen assimilation pathway, resulting in greater nitrogen assimilates, chlorophyll, starch, sugars, and grain yield in transgenic lines than in the WT under suboptimal and optimal nitrogen conditions. OsAMT1;1 also enhanced overall plant growth, especially under suboptimal NH4 + levels. These results suggest that OsAMT1;1 has the potential for improving nitrogen use efficiency, plant growth, and grain yield under both suboptimal and optimal nitrogen fertilizer conditions.

Temperatures higher than the optimum negatively affects plant growth and development. Tolerance to high temperature is a complex process that involves several pathways. Understanding this process, especially in crops such as rice, is essential to prepare for predicted climate changes due to global warming. Here, we show that OsMYB55 is induced by high temperature and overexpression of OsMYB55 resulted in improved plant growth under high temperature and decreased the negative effect of high temperature on grain yield. Transcriptome analysis revealed an increase in expression of several genes involved in amino acids metabolism. We demonstrate that OsMYB55 binds to the promoter regions of target genes and directly activates expression of some of those genes including glutamine synthetase (OsGS1;2) glutamine amidotransferase (GAT1) and glutamate decarboxylase 3 (GAD3). OsMYB55 overexpression resulted in an increase in total amino acid content and of the individual amino acids produced by the activation of the above mentioned genes and known for their roles in stress tolerance, namely L-glutamic acid, GABA and arginine especially under high temperature condition. In conclusion, overexpression of OsMYB55 improves rice plant tolerance to high temperature, and this high tolerance is associated with enhanced amino acid metabolism through transcription activation.

Background and Purpose: The benefit of endovascular treatment (EVT) for large vessel occlusion in clinical practice in developing countries like China needs to be confirmed. The aim of the study was to determine whether the benefit of EVT for acute ischemic stroke in randomized trials could be generalized to clinical practice in Chinese population. Methods: We conducted a prospective registry of EVT at 111 centers in China. Patients with acute ischemic stroke caused by imaging-confirmed intracranial large vessel occlusion and receiving EVT were included. The primary outcome was functional independence at 90 days defined as a modified Rankin Scale score of 0 to 2. Outcomes of specific subgroups in the anterior circulation were reported and logistic regression was performed to predict the primary outcome. Results: Among the 1793 enrolled patients, 1396 (77.9%) had anterior circulation large vessel occlusion (median age, 66 [56–73] years) and 397 (22.1%) had posterior circulation large vessel occlusion (median age, 64 [55–72] years). Functional independence at 90 days was reached in 45% and 44% in anterior and posterior circulation groups, respectively. For anterior circulation population, underlying intracranial atherosclerotic disease was identified in 29% of patients, with higher functional independence at 90 days (52% versus 44%; P =0.0122) than patients without intracranial atherosclerotic disease. In the anterior circulation population, after adjusting for baseline characteristics, procedure details, and early outcomes, the independent predictors for functional independence at 90 days were age <66 years (odds ratio [OR], 1.733 [95% CI, 1.213–2.476]), time from onset to puncture >6 hours (OR, 1.536 [95% CI, 1.065–2.216]), local anesthesia (OR, 2.194 [95% CI, 1.325–3.633]), final modified Thrombolysis in Cerebral Infarction 2b/3 (OR, 2.052 [95% CI, 1.085–3.878]), puncture-to-reperfusion time ≤1.5 hours (OR, 1.628 [95% CI, 1.098–2.413]), and National Institutes of Health Stroke Scale score 24 hours after the procedure <11 (OR, 9.126 [95% CI, 6.222–13.385]). Conclusions: Despite distinct characteristics in the Chinese population, favorable outcome of EVT can be achieved in clinical practice in China. Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT03370939.