Programmed cell death is a genetically regulated process of cellular suicide at special time and position with endogenous or environmental induction signals for multicellular organisms. It plays an important role in plant development. In this paper, we introduce the different kinds of programmed cell death in plants, several model systems for research in this field, and describe the current advances in the regulatory mechanisms of developmental programmed cell death in plants.

A hallmark of flowering plants is sexual reproduction, with the embryo a key player. In double fertilization, the zygote (fertilized egg) first establishes its apical-basal polarity within the single cell. With cell division and differentiation, the proembryo forms a apical-basal axis and develops through pattern formation and organogenesis. Recent advances have shown that the whole process of embryogenesis is regulated by auxin at levels of biosynthesis, polar transport and signal transduction. In this review, we highlight our current understanding, mainly from studies in Arabidopsis, of the molecular mechanisms by which auxin controls embryogenesis. These mechanisms include the establishment of polarity of zygotes, apical-basal axis of embryos, differentiation of protoderm, transition of radial symmetry to bilateral symmetry, formation of hypophysis, shoot apical meristem and root apical meristem. In addition, we briefly introduce the embryogenesis process not regulated by auxin.

We used fractionation with cadmium (Cd) treatment to investigate the subcellular distribution of Cd in different organs of Artemisia selengensis. With 30 mg·kg^─1 Cd, Cd content was 2 to 3 times higher in leaves than in stems and roots; however, because of the smaller proportion of leaf biomass to total plant biomass, the amount of Cd in leaves was much less than that in stems or roots. Under the stress of this Cd concentration, the subcellular distribution ratio of Cd in leaves was 16:5:1 for cell walls, cytosole, and organelles. The retention of Cd in the cell walls is a major defense mechanism of leaves. The Cd content in cell walls and cytosole increased significantly with increasing additional Cd²⁺, but Cd content in organelles was still low. The stress of long-term Cd exposure or high Cd concentration causes serious harm or even death to a plant. A large amount of Cd is deposited in root vacuoles, for a detoxification effect for Cd stress.

Callose synthase gene GSL8 in Arabidopsis thaliana was knocked out by means of T-DNA insertion or RNA interference. Cell walls and root apical organization in seeds and seedlings of the knockout lines and wild-type were compared by using light and transmission electron microscopes. Gaps of various sizes were found to occur in cell walls in all knockout lines, and there were no plasma membranes in the gap regions to separate the neighboring cells. No normal quiescent center was established in the embryonic root apices during seed development in the T-DNA mutants. Furthermore, the quiescent center was demonstrated to disappear from the root apices of seedlings as the gene GSL8 was silenced by RNA interference. Based on these observations, it is suggested that the gene GSL8 was involved in the formation of cell wall as well as the establishment and maintenance of quiescent center in the root apex.

Sterols are major components of the eukaryotic membrane and play important roles in development processes. CYCLOPROPYL STEROL ISOMERASE1 (CPI1) encodes a plant-specific key enzyme in the plant sterol biosynthesis pathway. Only the CPI1 from Arabidopsis has been cloned and characterized. In this study, we identified single-copy CPI1 genes from algae to flowering plants. All CPI1 genes from land plants have a conserved gene structure and high protein sequence similarity ranging from 48% to 90%, with low protein sequence similarity between land plants and algae. Protein structure prediction revealed that all CPI1 proteins have a similar protein structure, with 7 transmembrane domains and 6 hydrophilic loops. RT-PCR revealed that the land plant CPI1 genes were constitutive expression genes. To investigate the function of CPI1 genes, CPI1 from Brachypodium distachyon was cloned and transformed into the Arabidopsis cpi1-1 mutant. The BdCPI1 gene could completely complement the function of AtCPI. Thus, our data for single copy number, conserved gene structures, protein structures, and gene expression patterns suggest that the functions of land plant CPI1 genes are highly conserved.

Schisandra sphenanthera is the third-class conservation of wild medicinal species. It is widely distributed in Qinling Mountains. We collected S. sphenanthera samples at 307 sampling points in 19 sampling sites and extracted deoxyschizandrin and γ-schizandrin by high-performance liquid chromatography. We used “fuzzy theory” to determine the association of deoxyschizandrin and γ-schizandrin content and 15 assessment factors, including climate, soil and topographic factors. Then we used the maximum entropy model to determine the weight of each factor. Finally, we estimated the spatial distribution of S. sphenanthera in Qinling Mountains by the weighted average method and GIS spatial analysis. The proportion of unsuitable, suitable and high-suitable habitat for S. sphenanthera in Qinling Mountains was 11.40%, 50.63%, and 37.97%, respectively. The high-suitable habitat are mainly located in southern Shaanxi, eastern Gansu, western Henan, Shennongjia in Hubei, and the surrounding area, with elevation 800 to 2 000 m.This habitat-suitability assessment model based on GIS and fuzzy logic could be used to accurately determine the habitat suitability of S. sphenanthera, quantify the area of suitable habitat and analyze the spatial distribution. This information would supply scientific evidence for the choice of GAP and construction and advice for protection and sustainable utilization of resources.

We investigated the rate of water ascent and time course of xylem pressure in response to light or darkness in the rehydrated resurrection plant Myrothamnus flabellifolia. The time for water to rise to the apex of an intact or detached desiccated twig was about 10 h, whereas the time for full recovery of the regulation of xylem pressure response to light or darkness was about 3 weeks. The recovery of the pressure regulation should be associated with the recovery and function of stomata in desiccated leaves after rehydration. In addition, the relaxation time of xylem pressure decline in response to light was significantly longer than that of xylem pressure ascent in response to darkness, so the regulation rate of the plant to transpiration increase induced by light was significantly lower than that to transpiration decline induced by darkness.

We used transmission electron microcopy to examine the process and ultrastructure of double fertilization in Oryza sativa. Such fertilization exhibits a unique fusing between the female and male nucleus. Direct fusion occurs only between the nuclear membranes of the female and male nucleus, instead of via mediating organelles, regardless of the presence of karyogamy between the sperm nucleus and egg cell nucleus or between the sperm nucleus and polar nucleus (secondary nucleus). Furthermore, the sperm nucleus attaches to the persistent synergid 3.5 h after pollination.

Rice (Oryza sativa) is one of the most important food crops in the world and a model plant for study of molecular developmental biology in monocots. Panicle morphology is an important component of rice production and has become a “hot” topic in genetic improvement and developmental biology research of rice. Multiple-grain rice is a mutant of spikelets, which can be divided into clustered-spikelet and multi-pistil types created by natural mutation, hybrid variation, and physical/chemical mutagenesis. As a new germplasm resource, multiple-grain rice can help to establish new materials, new varieties, and sterility propagation and help in research into mechanisms of rice flowering. Because of spike grain density, multiple-grain rice can be used for large-compound-grain rice breeding materials, improving spike grain density and grain number per spike, shortening spike length, ameliorating rice plant traits, enhancing resistance and increasing yield. Here, we summarize the features of multiple-grain rice, origin, genetic analysis, gene location and breeding utilization, and point out the future of this research, which should provide a reference for further researching multiple-grain rice.

As the primary intracellular calcium sensors, calmodulins regulate different cellular physiologic, growth and development processes by binding to different calmodulin-binding proteins. The IQ motif, IQxxxRGxxxR (Pfam 00612), is one of a few recognition motifs for calmodulins in calmodulin-binding proteins. As well as a few other proteins, 5 major families, including IQM, IQD, CAMTA, CNGC and myosin family, have been found to possess the IQ motif(s) in plants. Here, we review the research progress in plant IQ motif-containing calmodulin-binding proteins, including their type, structural characteristics and function, and prospects for future study.

Jasmonic acid (JA) is the specific phytohormone responding to plant wounding and plays a central function in both plant local and systemic wounding signaling. However, an 18-amino acid polypeptide system has been identified in tomato for initiating systemic JA production and defense gene expression in undamaged distal tissues. Arabidopsis At-PEPs (a class of short peptides) can activate transcription of the defense gene defensin (PDF1.2) and be induced by wounding, JA and ethylene, which are potentially connected to the wounding response. Both antagonistic and synergistic interactions occur between abscisic acid (ABA) and JA signaling in Arabidopsis. The deficiency in activation of JA-induced genes in ABA-deficient mutants indicates that ABA precedes or cooperates with JA in activating the defense response. In addition, plants have a JA-independent wounding signal pathway, overrepresented by RNase. We review recent advances in investigating the mechanism and signal transduction in the wounding response of plants.