Research progress on differentiation and regulation of plant chromoplasts.

Carotenoids, natural tetraterpenoids found abundantly in plants, contribute to the diverse colors of plant non-photosynthetic tissues and provide fragrance through their cleavage products, which also play crucial roles in plant growth and development. Understanding the synthesis, degradation, and storage pathways of carotenoids and identifying regulatory factors represents a significant strategy for enhancing plant quality. Chromoplasts serve as the primary plastids responsible for carotenoid accumulation, and their differentiation is linked to the levels of carotenoids, rendering them a subject of substantial research interest. The differentiation of chromoplasts involves alterations in plastid structure and protein import machinery. Additionally, this process is influenced by factors such as the ORANGE (OR) gene, Clp proteases, xanthophyll esterification, and environmental factors. This review shows the relationship between chromoplast and carotenoid accumulation by presenting recent advances in chromoplast structure, the differentiation process, and key regulatory factors, which can also provide a reference for rational exploitation of chromoplasts to enhance plant quality.

Construction and optimization of Green Infrastructure Network in mountainous cities: a case study of Fuzhou, China.

Green infrastructure networks enhance the protection and improvement of urban ecological environments, augment the efficiency and quality of ecosystem services, and furnish residents with healthier and more comfortable living conditions. Although previous research has investigated the construction or optimization methods of green infrastructure networks, these studies have been relatively isolated and lacking in case studies for mountainous cities. In the development of green infrastructure, mountainous cities must specifically consider the impact of terrain on network construction. Taking Fuzhou, a mountainous city in China, as an example, this study constructs and optimizes the green infrastructure network by employing morphological spatial pattern analysis, connectivity analysis, the Minimum Cumulative Resistance model, and circuit theory. These methodologies increase the connectivity of the Green Infrastructure within the study area, thereby promoting the health of the local ecosystem and creating conducive circumstances for the city's sustainable development. The findings reveal that: (1) Green infrastructure in Fuzhou takes up 5366.38 ha, constituting 21.76% of the study area, primarily situated in the northwest and south; (2) Fuzhou's Green Infrastructure network comprises 10 hubs and 17 corridors with a hub area of 1306.98 ha, predominantly distributed in the mountains encircling the city, including Meifeng Mountain, Gaogai Mountain, and Qingliang Mountain; (3) Based on optimization, the circuit centrality index categorizes hub importance into three protection levels, pinpointing nine crucial protected areas in the corridors and 680 areas requiring enhancement, including 68 areas for first-level improvement, 149 areas for second-level improvement, and 463 areas for third-level improvement. This research offers a methodological reference for constructing and optimizing green infrastructure networks in mountainous cities, providing both theoretical and practical foundations for optimizing green infrastructure networks in Fuzhou City.

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Given the facts that urban land is extremely limited and ecological environment protection is confronted with severe challenges, it is of great importance to effectively construct green infrastructure (GI) network and identify relatively important landscape ecological components. We identified and prioritized GI network centers in Fuzhou downtown area using the MSPA and the landscape connectivity evaluation. The least cost path method and gravity model were used to construct the potential corridors at multiple levels. The density analysis and blind area analysis were used to extract and prioritize the GI nodes and to obtain the optimized GI network. The results showed that the first-level GI network centers were mainly distributed in the north and south of Fuzhou downtown, while those in the central region were small and scattered. The comprehensive resistance of landscape was low in the periphery but high in the middle, with poor integral connectivity. The GI corridor system with existing corridors and potential corridors was employed to enhance the connectivity among network centers. Furthermore, the GI nodes were extracted to provide a "transfer station" for material circulation and energy flow, which could partly solve the problems including excessive substrate resistance and the long connection corridor in some areas. The spatial prioritization of GI elements could make the construction of GI network more scientific and also provide reference for the future planning period and construction timing of GI network in Fuzhou.

Screening of key genes responsible for Pennisetum setaceum 'Rubrum' leaf color using transcriptome sequencing.

Pennisetum setaceum 'Rubrum' is an ornamental grass plant that produces purple leaves in high-light environments and light purple or green leaves in low-light environments, the latter of which greatly reduces its aesthetic appeal. Therefore, we aimed to identify the key genes associated with leaf coloration and elucidate the molecular mechanisms involved in the color changes in P. setaceum 'Rubrum' leaves. We performed transcriptome sequencing of P. setaceum 'Rubrum' leaves before and after shading. A total of 19,043 differentially expressed genes were identified, and the numbers of upregulated and downregulated genes at T1 stage, when compared with their expression at the T0 stage, were 10,761 and 8,642, respectively. The possible pathways that determine P. setaceum 'Rubrum' leaf color included flavonoid biosynthesis, flavone and flavonol biosynthesis, and carotenoid biosynthesis. There were 31 differentially expressed genes related to chlorophyll metabolism, of which 21 were related to chlorophyll biosynthesis and 10 to chlorophyll degradation, as well as three transcription factors that may be involved in the regulation of chlorophyll degradation. There were 31 key enzyme genes involved in anthocyanin synthesis and accumulation in P. setaceum 'Rubrum' leaves, with four transcription factors that may be involved in the regulation of anthocyanin metabolism. The transcriptome data were verified and confirmed reliable by real-time fluorescence quantitative PCR analysis. These findings provide a genetic basis for improving leaf color in P. setaceum 'Rubrum.'

Nitrogen supply enhances the physiological resistance of Chinese fir plantlets under polyethylene glycol (PEG)-induced drought stress.

Water and nitrogen stresses are major constraints for agricultural and forest productivity. Although the effects of water scarcity or nitrogen stress on plant growth, physiology, and yield have been widely studied, few studies have assessed the combined effects of both stresses. In the present study, we investigated the effects of different nitrogen forms (NO3-N, NH4+-N, and a combination of NO3-N + NH4+-N) on antioxidant enzyme activity, osmotic regulatory substances, and nitrogen assimilation in Chinese fir (Cunninghamia lanceolata) plantlets under drought stress (induced by 10% polyethylene glycol). We found that different N ionic forms had different effects on drought-stressed plantlets. Nitrogen supply greatly increased the activities of superoxide dismutase (SOD), peroxidase (POD) and polyphenol oxidase (PPO) when plantlets were exposed to water stress. The malondialdehyde (MDA) contents significantly decreased under the NH4+ + water stress treatment. The proline (Pr) contents significantly increased in both the NO3-N and NH4+-N + water stress treatment. The nitrate reductase (NR) increased by 7.1% in the NO3- + water stress treatment, and the glutamine synthetase (GS), and the glutamate synthase (GOGAT) activity increased in all the nitrogen + water stress treatments. These results suggested that nitrogen supply could alleviate the adverse effects of drought stress on plants by enhancing antioxidant defense and improving nitrogen assimilation, while the effects on plant tolerance to drought stress varied with nitrogen ionic forms.

Effects of LED Light on Acacia Melanoxylon Bud Proliferation in Vitro and Root Growth ex Vitro.

This study examines the effects of light emitting diodes (LEDs) on tissue culture proliferation of Acacia melanoxylon plantlets among five different clones (FM1, FM2, FM4, FM5, and FM10). Shoot bud apex cuttings were transplanted onto Murashige and Skoog basal medium containing 0.1 mg L-1 6-benzyladenine and 0.5 mg L-1 naphthalene acetic acid and cultured in vitro for 40 days. Root growth was studied under different light intensities and photoperiods ex vitro. The bud proliferation coefficient was greatest under a light intensity of 45 µmol m-2 s-1 photosynthetic photon flux and photoperiod of 16 h light, but decreased as the light intensity increased. However, the greatest light intensity was beneficial for the growth of robust plantlets. Plantlets exposed to red and blue LED combinations grew tall and green, with a small number of roots. Plantlets also grew taller and some roots expanded under the longer photoperiod. Increased light intensity had positive effects on root number and rooting rate, and prolonged light greatly increased root number. Therefore, lower light intensity and a short photoperiod were beneficial for bud proliferation, while red/blue LED combinations, increased light intensity, and longer light illumination were beneficial for plantlet growth and root growth of Acacia melanoxylon.

Optimization of hormone combinations for root growth and bud germination in Chinese fir (Cunninghamia lanceolata) clone leaf cuttings.

In order to ascertain the optimal hormone combination for Chinese fir (Cunninghamia lanceolata) leaf cuttings, an L16(4)4 orthogonal test of 6-benzylaminopurine (6-BA), 1-naphthaleneacetic acid (NAA), and indole-3-butyric acid (IBA) (0, 10, 30, or 50 mg · L-1 of each exogenous hormone) immersion for 5, 10, 15, or 20 min was conducted. Callus initiation rate and rooting promotion rate were mainly affected by treatment time, root length increase by 6-BA concentration, and bud germination rate and plantlet formation rate by NAA concentration. The expected optimal combination for callus initiation rate was 50 mg · L-1 6-BA + 0 mg · L-1 NAA + 30 mg · L-1 IBA + 10 min; for rooting promotion rate, it was 0-10 mg · L-1 6-BA + 10 mg · L-1 NAA + 30 mg · L-1 IBA + 20 min; for bud germination rate, it was 50 mg · L-1 6-BA + 0-10 mg · L-1 NAA + 0-30 mg · L-1 IBA + 20 min; and for seedling formation rate for No. 4, it was 10 mg · L-1 6-BA + 10 mg · L-1 NAA + 0 mg · L-1 IBA + 20 min. Light microscopy image analysis revealed that a cluster of primordial cells was produced 40 days after cutting, and mastoid cells developed into peninsula cells in calli that were cultured for 50 days.

Genetic diversity and variation of Chinese fir from Fujian province and Taiwan, China, based on ISSR markers.

Genetic diversity and variation among 11 populations of Chinese fir from Fujian province and Taiwan were assessed using inter-simple sequence repeat (ISSR) markers to reveal the evolutionary relationship in their distribution range in this report. Analysis of genetic parameters of the different populations showed that populations in Fujian province exhibited a greater level of genetic diversity than did the populations in Taiwan. Compared to Taiwan populations, significant limited gene flow were observed among Fujian populations. An UPGMA cluster analysis showed that the most individuals of Taiwan populations formed a single cluster, whereas 6 discrete clusters were formed by each population from Fujian. All populations were divided into 3 main groups and that all 5 populations from Taiwan were gathered into a subgroup combined with 2 populations, Dehua and Liancheng, formed one of the 3 main groups, which indicated relative stronger relatedness. It is supported by a genetic structure analysis. All those results are suggesting different levels of genetic diversity and variation of Chinese fir between Fujian and Taiwan, and indicating different patterns of evolutionary process and local environmental adaption.

Ion Flux in Roots of Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook) under Aluminum Stress.

Chinese fir is a tall, fast-growing species that is unique to southern China. In Chinese fir plantations, successive plantings have led to a decline in soil fertility, and aluminum toxicity is thought to be one of the main reasons for this decline. In this study, Non-invasive Micro-test Technology was used to study the effect of aluminum stress on the absorption of 4 different ions in the roots of the Chinese fir clone FS01. The results are as follows: with increased aluminum concentration and longer periods of aluminum stress, the H+ ion flow gradually changed from influx into efflux; there was a large variation in the K+ efflux, which gradually decreased with increasing duration of aluminum stress; and 1 h of aluminum stress uniformly resulted in Ca2+ influx, but it changed from influx to efflux after a longer period of aluminum stress. Changes in the different concentrations of aluminum had the largest influence on Mg2+.

An improved agar-plate method for studying root growth and response of Arabidopsis thaliana.

Arabidopsis thaliana is a widely used model plant for plant biology research. Under traditional agar-plate culture system (TPG, traditional plant-growing), both plant shoots and roots are exposed to illumination, and roots are grown in sucrose-added medium. This is not a natural environment for the roots and may cause artifact responses. We have developed an improved agar-plate culture system (IPG, improved plant-growing) where shoots are illuminated but roots are grown in darkness without sucrose addition. Compared to TPG, IPG produced plants with significantly less total root length, lateral root length and root hair density, although their primary roots were longer. Root gravitropism, PIN2 (an auxin efflux carrier) abundance, H⁺ efflux or Ca²âº influx in root apexes, were weaker in IPG-grown roots than those in TPG-grown roots. We conclude that IPG offers a more natural way to study the root growth and response of Arabidopsis thaliana.

PIN2 is required for the adaptation of Arabidopsis roots to alkaline stress by modulating proton secretion.

Soil alkalinity is a widespread environmental problem that limits agricultural productivity. The hypothesis that an auxin-regulated proton secretion by plasma membrane H(+)-ATPase plays an important role in root adaption to alkaline stress was studied. It was found that alkaline stress increased auxin transport and PIN2 (an auxin efflux transporter) abundance in the root tip of wild-type Arabidopsis plants (WT). Compared with WT roots, the pin2 mutant roots exhibited much reduced plasma membrane H(+)-ATPase activity, root elongation, auxin transport, and proton secretion under alkaline stress. More importantly, roots of the pks5 mutant (PKS5, a protein kinase) lacking PIN2 (a pks5/pin2 double mutant) lost the previous higher proton-secretion capacity and higher elongation rate of primary roots under alkaline stress. By using Arabidopsis natural accessions with a high proton-secretion capacity, it was found that their PIN2 transcription abundance is positively related to the elongation rate of the primary root and proton-secretion capacity under alkaline stress. Taken together, our results confirm that PIN2 is involved in the PKS5-mediated signalling cascade under alkaline-stress and suggest that PIN2 is required for the adaptation of roots to alkaline stress by modulating proton secretion in the root tip to maintain primary root elongation.