No abstract

Despite the perceived importance of exudation to forest ecosystem function, few studies have attempted to examine the effects of elevated temperature and nutrition availability on the rates of root exudation and associated microbial processes. In this study, we performed an experiment in which in situ exudates were collected from Picea asperata seedlings that were transplanted in disturbed soils exposed to two levels of temperature (ambient temperature and infrared heater warming) and two nitrogen levels (unfertilized and 25 g N m À2 a À1). Here, we show that the trees exposed to an elevated temperature increased their exudation rates I (lg C g À1 root biomass h) in the unfertilized plots. The altered morphological and physiological traits of the roots exposed to experimental warming could be responsible for this variation in root exudation. Moreover, these increases in root-derived C were positively correlated with the microbial release of extracellular enzymes involved in the breakdown of organic N (R 2 = 0.790; P = 0.038), which was coupled with stimulated microbial activity and accelerated N transformations in the unfertilized soils. In contrast, the trees exposed to both experimental warming and N fertilization did not show increased exudation rates or soil enzyme activity, indicating that the stimulatory effects of experimental warming on root exudation depend on soil fertility. Collectively, our results provide preliminary evidence that an increase in the release of root exudates into the soil may be an important physiological adjustment by which the sustained growth responses of plants to experimental warming may be maintained via enhanced soil microbial activity and soil N transformation. Accordingly, the underlying mechanisms by which plant root-microbe interactions influence soil organic matter decomposition and N cycling should be incorporated into climate-carbon cycle models to determine reliable estimates of long-term C storage in forests.

The CRISPR/Cas system has been extensively applied to make precise genetic modifications in various organisms. Despite its importance and widespread use, large-scale mutation screening remains time-consuming, labour-intensive and costly. Here, we describe a cheap, practicable and high-throughput screening strategy that allows parallel screening of 96 × N (N denotes the number of targets) genome-modified sites. The strategy simplified and streamlined the process of next-generation sequencing (NGS) library construction by fixing the bridge sequences and barcoding primers. We also developed Hi-TOM (available at http://www.hi-tom.net/hi-tom/), an online tool to track the mutations with precise percentage.Analysis of the samples from rice, hexaploid wheat and human cells reveals that the Hi-TOM tool has high reliability and sensitivity in tracking various mutations, especially complex chimeric mutations that frequently induced by genome editing. Hi-TOM does not require specially design of barcode primers, cumbersome parameter configuration or additional data analysis. Thus, the streamlined NGS library construction and comprehensive result output make Hi-TOM particularly suitable for high-throughput identification of all types of mutations induced by CRISPR/Cas systems.

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated endonuclease 9 (CRISPR/Cas9) system has emerged as a promising technology for specific genome editing in many species. Here we constructed one vector targeting eight agronomic genes in rice using the CRISPR/Cas9 multiplex genome editing system. By subsequent genetic transformation and DNA sequencing, we found that the eight target genes have high mutation efficiencies in the T generation. Both heterozygous and homozygous mutations of all editing genes were obtained in T plants. In addition, homozygous sextuple, septuple, and octuple mutants were identified. As the abundant genotypes in T transgenic plants, various phenotypes related to the editing genes were observed. The findings demonstrate the potential of the CRISPR/Cas9 system for rapid introduction of genetic diversity during crop breeding.

1. Fine root traits vary greatly with environmental changes, but the understanding of root trait variation and its drivers is limited over broad geographical scales, especially for ectomycorrhizal (ECM)-dominated conifers in alpine forests. Herein, the covariation patterns of and environmental controls for fine root traits among ECM-dominated conifers were examined to test whether and how climate and soil nutrients differentially affect fine root trait variations. 2. Eight traits of first-and second-order roots were measured, that is, root diameter (RD), specific root length (SRL), branching intensity (BRI), root tissue density (RTD), mycorrhizal colonization rate (MCR) and concentrations of carbon (C), nitrogen (N) and phosphorus (P), across 76 alpine coniferous populations on the eastern Tibetan Plateau, China. 3. Our results showed that variations of the fine root traits fell into two major dimensions: the first dimension (32.39% of the total variance) was mainly represented by RD and SRL, potentially conveying a trade-off between root life span and efficiency of resource foraging; the second dimension (23.70% of the variance) represented coordinated variation for root nutrients (i.e. N and P) and RTD, which depicts the conservation-acquisition trade-off in resource uptake, that is, root economic spectrum. Variations in RD and SRL were mainly driven by climatic variables, characterized by a significant increase in RD and a decrease in SRL with increasing mean annual precipitation. In contrast, variations in fine root nutrients (i.e. N and P) and RTD were primarily driven by soil fertility, showing a significant increase in root N and P concentrations but a decrease in RTD with increasing soil resource levels. 4. Synthesis. Our study clearly shows two distinct dimensions of the variation of fine root traits in ECM-dominated alpine coniferous forests, providing further evidence of the inherent multidimensionality of root traits. Moreover, our findings highlight different roles of climatic and soil variables in driving the variation of fine root traits, potentially leading to the multidimensionality of root traits. This | 2545

Grain yield is one of the most important and complex trait for genetic improvement in crops; it is known to be controlled by a number of genes known as quantitative trait loci (QTLs). In the past decade, many yield-contributing QTLs have been identified in crops. However, it remains unclear whether those QTLs confer the same yield performance in different genetic backgrounds. Here, we performed CRISPR/Cas9-mediated QTL editing in five widely-cultivated rice varieties and revealed that the same QTL can have diverse, even opposing, effects on grain yield in different genetic backgrounds.

No abstract

Rice (Oryza sativa L.) seed serves as a major food source for over half of the global population. Though it has been long recognized that phosphorylation plays an essential role in rice seed development, the phosphorylation events and dynamics in this process remain largely unknown so far. Here, we report the first large scale identification of rice seed phosphoproteins and phosphosites by using a quantitative phosphoproteomic approach. Thorough proteomic studies in pistils and seeds at 3, 7 days after pollination resulted in the successful identification of 3885, 4313 and 4135 phosphopeptides respectively. A total of 2487 proteins were differentially phosphorylated among the three stages, including Kip related protein 1, Rice basic leucine zipper factor 1, Rice prolamin box binding factor and numerous other master regulators of rice seed development. Moreover, differentially phosphorylated proteins may be extensively involved in the biosynthesis and signaling pathways of phytohormones such as auxin, gibberellin, abscisic acid and brassinosteroid. Our results strongly indicated that protein phosphorylation is a key mechanism regulating cell proliferation and enlargement, phytohormone biosynthesis and signaling, grain filling and grain quality during rice seed development. Overall, the current study enhanced our understanding of the rice phosphoproteome and shed novel insight into the regulatory mechanism of rice seed development.