A high-quality rice activation tagging population has been developed and screened for drought-tolerant lines using various water stress assays. One drought-tolerant line activated two rice glutamate receptor-like genes. Transgenic overexpression of the rice glutamate receptor-like genes conferred drought tolerance to rice and Arabidopsis. Rice (Oryza sativa) is a multi-billion dollar crop grown in more than one hundred countries, as well as a useful functional genetic tool for trait discovery. We have developed a population of more than 200,000 activation-tagged rice lines for use in forward genetic screens to identify genes that improve drought tolerance and other traits that improve yield and agronomic productivity. The population has an expected coverage of more than 90 % of rice genes. About 80 % of the lines have a single T-DNA insertion locus and this molecular feature simplifies gene identification. One of the lines identified in our screens, AH01486, exhibits improved drought tolerance. The AH01486 T-DNA locus is located in a region with two glutamate receptor-like genes. Constitutive overexpression of either glutamate receptor-like gene significantly enhances the drought tolerance of rice and Arabidopsis, thus revealing a novel function of this important gene family in plant biology.

Histone variants alter the nucleosome structure and play important roles in chromosome segregation, transcription, DNA repair, and sperm compaction. Histone H3 is encoded by many genes in most eukaryotic species and is the histone that contains the largest variety of posttranslational modifications. Compared with the metazoan H3 variants, little is known about the complex evolutionary history of H3 variants proteins in plants. Here, we study the identification, evolutionary, and expression analyses of histone H3 variants from genomes in major branches in the plant tree of life. Firstly we identified all the histone three related (HTR) genes from the examined genomes, then we classified the four groups variants: centromeric H3, H3.1, H3.3 and H3-like, by phylogenetic analysis, intron information, and alignment. We further demonstrated that the H3 variants have evolved under strong purifying selection, indicating the conservation of HTR proteins. Expression analysis revealed that the HTR has a wide expression profile in maize and rice development and plays important roles in development.

The aim of this study was to investigate the physiological basis and molecular mechanism of genotypic variation in drought response of maize seedlings. Comparative physiological and proteomic analyses were conducted in the leaves of droughttolerant Liyu 35 (LY) and drought-sensitive Denghai 605 (DH) maize genotype seedlings. Drought induced a significant decrease of relative water content and osmotic potential of leaves, length and volume of roots, and total dry weight, but significantly increased malondialdehyde in DH seedlings. However, root dry weight , proline content and antioxidant enzyme activities increased more in LY than in DH. Forty-two spots in LY and 17 spots in DH that showed significant abundance variations were identified by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry. These drought-responsive proteins were mainly involved in biological processes of photosynthesis, defense and oxidative stress, carbohydrate and energy metabolism, protein synthesis and processing, and cell wall biogenesis and degradation. Among them, proteins involved in defense and oxidative stress, and protein synthesis and processing were largely enriched in the LY genotype, which may contribute to a natural variation of drought resistance between LY and DH genotypes. The altered protein abundance and corresponding physiological-biochemical response shed some light on molecular mechanisms related to drought tolerance in drought-tolerant maize and provide key candidate proteins for genetic improvement of maize.

Acer pictum subsp. mono is a colored leaf tree with vital ornamental and economic value. However, insufficient color change and early leaf fall in cities restrict its ornamental value. In this research, green and red leaves from wild A. p. subsp. mono were collected to study the regulatory mechanisms of leaf color change. Through the determination of plant physiological indexes, we found that the photosynthetic pigment content in red leaves decreased significantly compared with green leaves, while the anthocyanin content and antioxidant activity increased significantly compared with green leaves during the leaf color change process. Using transcriptome sequencing, we found more than 5500 differentially expressed genes, most of which were up-regulated. Many of the differentially expressed genes are involved in the anthocyanin metabolic pathway. The expression patterns of 15 key genes were investigated by quantitative real-time polymerase chain reaction. Among these genes, AmDFR and PAL1 are significant genes involved in the anthocyanin metabolic pathway, and CIPKs2, CIPKs6, CMLs1, CMLs38, AmGST1, AmGST2, GPX3, CBF, AmAPX, AmSOD, POD5, AmGR, and PSBY might be stress response genes that indirectly regulated the anthocyanin accumulation. The results showed that these genes play vital roles in the leaf color change of A. p. subsp. mono. This research will be helpful in further study of the molecular regulatory mechanisms of leaf color change and for the improvement of colored leaf plants.

Acer rubrum L., a widely used ornamental colored-leaf tree species, has great utility in both residential and urban landscaping. However, unsuitable environmental conditions tend to reduce the intensity of color change, greatly reducing the ornamental value of this species. Here, we investigated the discoloration of A. rubrum leaves from red to green during maturation. We first quantified leaf-color change in the L*, a*, b* color space, and found the most noticeable difference in the a* value, which changed from positive (more red) to negative (more green). In green leaves, photosynthetic pigment content was four-fold greater than that in red leaves, and anthocyanin content was significantly lowed (a 78.33% decrease). Consistent with this, levels of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as non-photochemical quenching, were significantly higher in red leaves. The activity levels of phenylalanine ammonia lyase (PAL), an initial enzyme in the anthocyanin synthesis pathway, were significantly positively correlated with anthocyanin accumulation. In contrast, polyphenol oxidase (PPO) enzyme activity was not correlated with any with other indicators. Transcriptome sequencing identified 2,161 differentially expressed genes (DEGs) between the red leaves and the green leaves (1,253 upregulated). Some of these DEGs (e.g., 4-coumarate: coenzyme A ligase (4CL), anthocyanidin synthase (ANS), phenylalanine ammonia lyase (PAL), flavonol synthase (FLS), chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR), and flavanone 3-hydroxylase (F3H)) encoded important enzymes in the anthocyanin metabolic pathway, while others (e.g., MYB111 (EZV62_000212), MYB12 (EZV62_010323), and bHLH3 (EZV62_023045)) regulated anthocyanin accumulation. Our results have led to a clearer understanding of the physiological and genetic mechanisms underlying leaf-color change in A. rubrum, and provide a basis from which to improve the ornamental properties of colored-leaf tree species.