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Breeding for strong root systems is an important strategy for improving drought avoidance in rice. To clone genes responsible for strong root traits, an upland rice introgression line IL392 with thicker and longer roots than the background parent lowland rice Yuefu was selected. A quantitative trait locus (QTL), qRT9, controlling root thickness and root length was detected under hydroponic culture using 203 F2:3 populations derived from a cross between Yuefu and IL392. The qRT9 locus explained 32.5% and 28.1% of the variance for root thickness and root length, respectively. Using 3185 F2 plants, qRT9 was ultimately narrowed down to an 11.5 kb region by substitution mapping. One putative basic helix-loop-helix (bHLH) transcription factor gene, LOC_Os09g28210 (named OsbHLH120), is annotated in this region. Sequences of OsbHLH120 in 11 upland rice and 13 lowland rice indicated that a single nucleotide polymorphism (SNP) at position 82 and an insertion/deletion (Indel) at position 628-642 cause amino acid changes and are conserved between upland rice and lowland rice. Phenotypic analysis indicated that the two polymorphisms were significantly associated with root thickness and root length under hydroponic culture. Quantitative real-time PCR showed that OsbHLH120 was strongly induced by polyethylene glycol (PEG), salt, and abscisic acid, but higher expression was present in IL392 roots than in Yuefu under PEG and salt stress. The successfully isolated locus, qRT9, enriches our knowledge of the genetic basis for drought avoidance and provides an opportunity for breeding drought avoidance varieties by utilizing valuable genes in the upland rice germplasm. [ABSTRACT FROM AUTHOR]

This study synthesized three different coatings using multi-arc ion coating technology: AlCrN, AlCrBN monolayer, and AlCrN/AlCrBN nano-multilayer coatings. A comparative investigation was conducted on the microstructure, mechanical performance, thermal stability, and oxidation properties of coatings. The results indicate the AlCrN, AlCrBN, and AlCrN/AlCrBN nano-multilayer coatings consist of face-centered cubic solid solution fcc-(Cr, Al)N phase. AlCrN/AlCrBN nano-multilayer coatings also exhibit better thermal stability and oxidation resistance than AlCrN and AlCrBN monolayer coatings. The AlCrN/AlCrBN nano-multilayer coatings have a dense, protective, Al 2 O 3 layer formed during high-temperature oxidation. During high-temperature oxidation, the AM (amplitude modulation) decomposition of the AlCrN and AlCrBN monolayers in the AlCrN/AlCrBN nanolayers is inhibited by the structure of the multilayer coatings. The formation of dense oxides on the surface prevents the diffusion of Al and Cr atoms to the outside and prevents the diffusion of oxygen from the outside to the inside of the AlCrN/AlCrBN nanolayers. • AlCrN/AlCrBN nano-multilayer coating was deposited by cathodic arc evaporation. • The microstructure, thermal stability, and oxidation resistance were investigated. • AlCrN/AlCrBN coating exhibits enhanced thermal stability compared with AlCrN and AlCrBN coatings. • The multilayer structure of the AlCrN/AlCrBN is effective in preventing oxidation. [ABSTRACT FROM AUTHOR]

Background: microRNAs (miRNAs) are important regulators in plant growth and development. miR159 is a conserved miRNA among different plant species and has various functions in plants. Studies on miR159 are mostly done on model plant, Arabidopsis thaliana. In rice, studies on miR159 were either based upon genome-wide expression analyses focused upon responses to different nitrogen forms and abiotic stress or upon phenotypic studies of transgenic plants overexpressing its precursor. STTM (Short Tandem Target Mimic) is an effective tool to block the activity of endogenous mature miRNA activity in plant. Therefore, specific roles of miR159 in rice could be explored by down regulating miR159 through STTM. Results: In this study, expression of mature miR159 was successfully suppressed by STTM which resulted in the increased expressions of its two targets genes, OsGAMYB and OsGAMYBL1 (GAMYB-LIKE 1). Overall, STTM159 plants exhibited short stature along with smaller organ size and reduction in stem diameter, length of flag leaf, main panicle, spikelet hulls and grain size. Histological analysis of stem, leaf and mature spikelet hull showed the reduced number of small vascular bundles (SVB), less number of small veins (SV) between two big veins (LV) and less cell number in outer parenchyma. Gene Ontology (GO) enrichment analysis of differentially expressed genes between wild type plants and STTM159 transgenic plants showed that genes involved in cell division, auxin, cytokinin (CK) and brassinosteroids (BRs) biosynthesis and signaling are significantly down-regulated in STTM159 plants. Conclusion: Our data suggests that in rice, miR159 positively regulates organ size, including stem, leaf, and grain size due to the promotion of cell division. Further analysis from the RNA-seq data showed that the decreased cell divisions in STTM159 transgenic plants may result, at least partly from the lower expression of the genes involved in cell cycle and hormone homeostasis, which provides new insights of rice miR159-specific functions. [ABSTRACT FROM AUTHOR]

Background The inferior spikelets are defined to be those at portions where the grains receive less photosynthetic products during the seed development. The typical inferior spikelets are physically located on the proximal secondary branches in a rice panicle and traditionally characterized by a later flowering time and a slower grain-filling rate, compared to those socalled superior spikelets. Grains produced on the inferior spikelets are consequently underdeveloped and lighter in weight than those formed on the superior spikelets. MicroRNAs (miRNAs) are recognized as key players in regulating plant development through posttranscriptional gene regulations. We previously presented the evidence that miRNAs may influence grain-filling rate and played a role in determining the grain weight and yield in rice. Results In this study, further analyses of the expressed small RNAs in superior and inferior spikelets were conducted at five distinct developmental stages of grain development. Totally, 457 known miRNAs and 13 novel miRNAs were analyzed, showing a differential expression of 141 known miRNAs between superior and inferior spikelets with higher expression levels of most miRNAs associated with the superior than the inferior spikelets during the early stage of grain filling. Genes targeted by those differentially expressed miRNAs (i.e. miR156, miR164, miR167, miR397, miR1861, and miR1867) were recognized to play roles in multiple developmental and signaling pathways related to plant hormone homeostasis and starch accumulation. Conclusions Our data established a complicated link between miRNA dynamics and the traditional role of hormones in grain filling and development, providing new insights into the widely accepted concepts of the so-called superior and inferior spikelets in rice production. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are upstream gene regulators of plant development and hormone homeostasis through their directed cleavage or translational repression of the target mRNAs, which may play crucial roles in rice grain filling and determining the final grain weight and yield. In this study, high-throughput sequencing was performed to survey the dynamic expressions of miRNAs and their corresponding target genes at five distinct developmental stages of grain filling. In total, 445 known miRNAs and 45 novel miRNAs were detected with most of them expressed in a developmental stage dependent manner, and the majority of known miRNAs, which increased gradually with rice grain filling, showed negatively related to the grain filling rate. Detailed expressional comparisons revealed a clear negative correlation between most miRNAs and their target genes. It was found that specific miRNA cohorts are expressed in a developmental stage dependent manner during grain filling and the known functions of these miRNAs are involved in plant hormone homeostasis and starch accumulation, indicating that the expression dynamics of these miRNAs might play key roles in regulating rice grain filling. [ABSTRACT FROM AUTHOR]