The Separation Mechanism of Bamboo Bundles at Cellular Level

Bamboo bundles with linear cracks were produced using mechanical treatments that were more environmentally friendly and more efficient than chemical decomposition and steam explosion. This study presented the separation mechanism by analyzing the structure, micro-mechanical properties and chemical constituent of bamboo bundles at the cellular level. The micro X-ray tomography technology (u-CT) morphology of bamboo and bamboo bundles presented that the separation of bamboo bundles was caused by crack propagation, which was related to the structure of the cell types in bamboo. Field emission scanning microscopy (SEM) was performed to observe the appearance of bamboo bundles at the cellular level, which illustrated that the cracks were prone to grow in the middle lamella (ML) in fiber cells and parenchymal cells. The nanoindentation technique and Raman microscopy was used to illustrate that the middle lamella (ML)with low indentation moduli and high lignin content was the weak structure in bamboo. This is interpreted as how the structure and mechanical properties contributed to the separation of the bamboo

The B-box family gene STO (BBX24) in Arabidopsis thaliana regulates flowering time in different pathways.

Flowering at the appropriate time is crucial for reproductive success and is strongly influenced by various pathways such as photoperiod, circadian clock, FRIGIDA and vernalization. Although each separate pathway has been extensively studied, much less is known about the interactions between them. In this study we have investigated the relationship between the photoperiod/circadian clock gene and FRIGIDA/FLC by characterizing the function of the B-box STO gene family. STO has two B-box Zn-finger domains but lacks the CCT domain. Its expression is controlled by circadian rhythm and is affected by environmental factors and phytohormones. Loss and gain of function mutants show diversiform phenotypes from seed germination to flowering. The sto-1 mutant flowers later than the wild type (WT) under short day growth conditions, while over-expression of STO causes early flowering both in long and short days. STO over-expression not only reduces FLC expression level but it also activates FT and SOC1 expression. It also does not rely on the other B-box gene CO or change the circadian clock system to activate FT and SOC1. Furthermore, the STO activation of FT and SOC1 expression is independent of the repression of FLC; rather STO and FLC compete with each other to regulate downstream genes. Our results indicate that photoperiod and the circadian clock pathway gene STO can affect the key flowering time genes FLC and FT/SOC1 separately, and reveals a novel perspective to the mechanism of flowering regulation

Auxin guides germ-cell specification in Arabidopsis anthers

International audienceSignificance Germ cells (GCs) (i.e., the cells that are committed to meiosis and gametogenesis) are key carriers for eukaryotes to complete their life cycle, transmitting their genetic information from one generation to the next while generating variations to integrate environmental changes. Compared to what has been known in animals, very little is known about how the GCs in plants are segregated from somatic cells. This work demonstrates that auxin is a key factor guiding GC specification in Arabidopsis anthers. Local auxin biosynthesis interacts with the transcription of SPOROCYTELESS/NOZZLE and a progressive GC specification itself to form a dynamic feedback circuit that ensures the completion of GC specification

Over-expression of <i>STO</i> promotes <i>FT</i> and <i>SOC1</i> expression independent of <i>FLC</i> repression.

<p>The level of <i>STO</i> (A), <i>FT</i> (B) and <i>SOC1</i> (C) expression in eight-day-old seedlings of the indicated genotypes. In the analysis, the data from STO-OE/flc/FRI-4 and -15 were compared to that of flc/FRI, while the data for STO-OE/FLC/FRI-11 was compared to that of FRI. Data from three independent replicates are shown, with <i>UBQ10</i> used as a control. (D) The number of rosette leaves in each indicated genotype at the time of flowering. All seedlings and mature plants were grown in SD. ** means p<0.01 in TTEST.</p

<i>sto-1</i> and <i>STO-OE</i> show diverse phenotypes.

<p>Col, <i>sto-1</i> and <i>STO-OE</i> were grown under SD conditions and different growth characteristics analyzed. (A) Seed germination as a percentage of total seeds analyzed; (B) hypocotyl length; (C) and (E) Seedling growth as measured by average hypocotyl length (<i>n</i> = 20–30) after 5 d on1/2 MS plates treated with BL (0–1000 nM) in SD; (D) and (F) Seedling growth as measured by average hypocotyl length (<i>n</i> = 20–30) after treatment with ACC (0–10 µM) for 3.5 days in darkness; (G) Appearance of adult rosette leaves on both adaxial and abaxial surfaces, with arrows indicating the position of leaf serration; (H–K) Flowering time of Col, <i>sto-1</i> and <i>STO-OE</i> in LD and SD conditions. The average number of rosette leaves in LD (J) and SD (K) was also calculated (<i>n</i> = 15–28, * means p<0.05 and ** means p<0.01 in TTEST).</p

Over-expression of <i>STO</i> promotes <i>FT</i> and <i>SOC1</i> expression independent of <i>CO</i> or <i>CCA1.</i>

<p>The level of <i>CCA1</i> (A), <i>CO</i> (B), <i>FT</i> (C) and <i>SOC1</i> (D) expression in eight-day-old seedlings under SD conditions. Data from two independent replicates are shown, with <i>UBQ10</i> used as a control. White and black bars represent the light and dark periods, respectively.</p

Gain-of-function of the 1-aminocyclopropane-1-carboxylate synthase gene ACS1G induces female flower development in cucumber gynoecy

Unisexual flowers provide a useful system for studying plant sex determination. In cucumber (Cucumis sativus L.), three major Mendelian loci control unisexual flower development, Female (F), androecious [a; 1-aminocyclopropane-1-carboxylate {ACC} synthase 11, acs11], and Monoecious (M; ACS2), referred to here as the Female, Androecious, Monoecious (FAM) model, in combination with two genes, gynoecious (g, the WIP family C2H2 zinc finger transcription factor gene WIP1) and the ethylene biosynthetic gene ACC oxidase 2 (ACO2). The F locus, conferring gynoecy and the potential for increasing fruit yield, is defined by a 30.2-kb tandem duplication containing three genes. However, the gene that determines the Female phenotype, and its mechanism, remains unknown. Here, we created a set of mutants and revealed that ACS1G is responsible for gynoecy conferred by the F locus. The duplication resulted in ACS1G acquiring a new promoter and expression pattern; in plants carrying the F locus duplication, ACS1G is expressed early in floral bud development, where it functions with ACO2 to generate an ethylene burst. The resulting ethylene represses WIP1 and activates ACS2 to initiate gynoecy. This early ACS1G expression bypasses the need for ACS11 to produce ethylene, thereby establishing a dominant pathway for female floral development. Based on these findings, we propose a model for how these ethylene biosynthesis genes cooperate to control unisexual flower development in cucumber