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"Qu, Li-Jia"
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إحضار الكتب المقدسة
عاش النبيل كو في بلدة تونغتايفو كان رجلا طيبا يحب الخير وعرض أن يستضيف سان تسانغ وتلاميذه لفترة طويلة، ولكنهم رفضوا رغم إلحاح عائلة النبيل؛ فلم يجدوا بدا من توديعهم. وما إن غادر سان تسانغ وتلاميذه حتى تعرض بيت النبيل للسرقة، وقتل النبيل كو، فأضمرت زوجته الضغينة لسان تسانغ وتلاميذه لأنهم لم يوافقوا على البقاء رغم الإلحاح عليهم، واتهمت الزوجة سان تسانغ وتلاميذه زورا بارتكاب الجريمة، وقدمت دعوى لمقاضاتهم. وفي طريق اللصوص للفرار، أرادوا سرقة سان تسانغ وتلاميذه أيضا، ولكن وو كونغ قبض عليهم، وحينما التقى سان تسانغ وتلاميذه بالضباط والجنود الذين جاؤوا لملاحقتهم، حدث سوء فهم أدى لاتهام سان تسانغ وتلاميذه.
Book
Pollen tube integrity regulation in flowering plants
Unlike in animals, sperm in flowering plants are immotile and they are embraced as passive cargoes by a pollen tube which embarks on a long journey in the pistil to deliver them to the female gametophyte for fertilization. How the pollen tube switches from a rapid polarized growth towards its target to an abrupt disintegration for sperm cell release inside the female gametophyte is puzzling. Recent studies have shown that members of the Catharanthus roseus RLK1-like (CrRLK1L) receptor kinase family and their ligands, 5-kDa cysteine-rich peptide rapid alkalinization factors (RALFs), engage in an intricate balancing act involving autocrine and paracrine signaling to maintain pollen tube growth and induce timely tube rupture at the spatially confined pollen tube–female gametophyte interface. Here, we review recent progress related to pollen tube integrity control, mainly focusing on the molecular understanding of signaling as well as intracellular signaling nodes in Arabidopsis. Some missing links and future perspectives are also discussed.
Journal Article
Targeted mutagenesis in rice using CRISPR-Cas system
Genome editing of model organisms is essential for gene function analysis and is thus critical for human health and agricultural production. The current technolo- gies used for genome editing include ZFN （zinc-finger nuclease）, meganucleases, TALEN （Transcription activa- tor-like effector nucleases）, etc. [1]. These technologies can generate double stranded breaks （DSBs） to either disrupt gene function through generation of premature stop codons by non-homologous end joining （NHEJ） pathway, or to facilitate gene targeting through homolo- gous recombination （HR） with an incoming template. Recently, a new technology for genome editing, CRISPR （Clustered Regularly Interspaced Short Palindromic Re- peats）/Cas （CRISPR-associated） systems, has been de- veloped [2]. CRISPR/Cas systems are adaptive defense systems in prokaryotic organisms to fight against alien nucleic acids [3]. The spacer sequences acquired from foreign DNA are positioned between host repeats, and transcribed together as CRISPR RNA （crRNA）. In the type II CRISPR system, a single nuclease Cas9, guided by a dual-crRNA：tracrRNA, is sufficient to cleave cog- nate DNA homologous to the spacer [2]. Efficient cleav- age also requires the presence of protospacer adjacent motif （PAM） 5＇-NGG-3＇ following the spacer sequence. The dual-crRNA：tracrRNA has been further streamlined to a single RNA chimera, called sgRNA （single guide RNA） [2]. Compared with protein-guided technologies, CRISPR/Cas system is much easier to implement, as only short guide RNAs need to be customized to target the genes of interest. Up to now, the CRISPR/Cas sys- tem has been successfully applied to efficient genome editing in many eukaryotic organisms including human [1], mice [4], zebra fish [5], fly [6], worm [7], and yeast [8]. However, the application of CRISPR/Cas system in plants has not been reported. Rice （Oryza sativa L.） is a major staple crop in the grass family （Poaceae）, feed- ing half of the world＇s population.
Journal Article
Crystal structure of PXY-TDIF complex reveals a conserved recognition mechanism among CLE peptide-receptor pairs
Plants can achieve amazing lifespans because of their continuous and repetitive formation of new organs by stem cells present within meristems. The balance between proliferation and differentiation of meristem cells is large- ly regulated by the CLAVATA3/ENDOSPERM SURROUNDING REGION （CLE） peptide hormones. One of the well-characterized CLE peptides, CLE41/TDIF （tracheary elements differentiation inhibitory factor）, functions to suppress tracheary element differentiation and promote procambial cell proliferation, playing important roles in vascular development and wood formation. The recognition mechanisms of TDIF or other CLE peptides by their respective receptors, however, remain largely elusive. Here we report the crystal structure of TDIF in complex with its receptor PXY, a leucine-rich repeat receptor kinase （LRR-RK）. Our structure reveals that TDIF mainly adopts an ＂t＇l＂-like conformation binding to the inner surface of the LRR domain of PXY. Interaction between TDIF and PXY is predominately mediated by the relatively conserved amino acids of TDIF. Structure-based sequence alignment showed that the TDIF-interacting motifs are also conserved among other known CLE receptors. Our data provide a structural template for understanding the recognition mechanism of CLE peptides by their receptors, offering an op- portunity for the identification of receptors of other uncharacterized CLE peptides.
Journal Article
Arabidopsis pollen tube integrity and sperm release are regulated by RALF-mediated signaling
In flowering plants, fertilization requires complex cell-to-cell communication events between the pollen tube and the female reproductive tissues, which are controlled by extracellular signaling molecules interacting with receptors at the pollen tube surface. We found that two such receptors in Arabidopsis, BUPS1 and BUPS2, and their peptide ligands, RALF4 and RALF19, are pollen tube–expressed and are required to maintain pollen tube integrity. BUPS1 and BUPS2 interact with receptors ANXUR1 and ANXUR2 via their ectodomains, and both sets of receptors bind RALF4 and RALF19. These receptor-ligand interactions are in competition with the female-derived ligand RALF34, which induces pollen tube bursting at nanomolar concentrations. We propose that RALF34 replaces RALF4 and RALF19 at the interface of pollen tube–female gametophyte contact, thereby deregulating BUPS-ANXUR signaling and in turn leading to pollen tube rupture and sperm release.
Journal Article
Arabidopsis RAP2.2 plays an important role in plant resistance to Botrytis cinerea and ethylene responses
• Ethylene plays a crucial role in plant resistance to necrotrophic pathogens, in which ETHYLENE RESPONSE FACTORs (ERFs) are often involved. • Here, we evaluated the role of an ERF transcription factor, RELATED TO AP2 2 (RAP2.2), in Botrytis resistance and ethylene responses in Arabidopsis. We analyzed the resistance of transgenic plants overexpressing RAP2.2 and the T‐DNA insertion mutant to Botrytis cinerea. We assessed its role in the ethylene signaling pathway by molecular and genetic approaches. • RAP2.2‐overexpressing transgenic plants showed increased resistance to B. cinerea, whereas its T‐DNA insertion mutant rap2.2‐3 showed decreased resistance. Overexpression of RAP2.2 in ethylene insensitive 2 (ein2) and ein3 ein3‐like 1 (eil1) mutants restored their resistance to B. cinerea. Both ethylene and Botrytis infection induced the expression of RAP2.2 and the induction was disrupted in ein2 and ein3 eil1 mutants. We identified rap2.12‐1 as a T‐DNA insertion mutant of RAP2.12, the closest homolog of RAP2.2. The hypocotyls of rap2.2‐3 rap2.12‐1 double mutants showed ethylene insensitivity. The constitutive triple response in constitutive triple response1 (ctr1) was partially released in the rap2.2‐3 rap2.12‐1 ctr1 triple mutants. • Our findings demonstrate that RAP2.2 functions as an important regulator in Botrytis resistance and ethylene responses.
Journal Article
Cysteine-rich peptides promote interspecific genetic isolation in Arabidopsis
Pollen tubes, which carry plant sperm, need to grow from where they land in the flower to where the ovule is. Zhong et al. now show how pollen from related plant species race to reach the ovule first. One set of fast-evolving peptide signals is tuned to speed up growth of conspecific pollen tubes. A related set of evolutionarily ancient peptides is tuned to attract all pollen tubes. Thus, fertilization is more likely to happen through conspecific pollen tubes, but a fail-safe system encourages even the laggards to get where they need to go. Science , this issue p. eaau9564 Competition between fast- and slow-growing pollen tubes driven by peptide signals favors conspecific fertilization. Reproductive isolation is a prerequisite for speciation. Failure of communication between female tissues of the pistil and paternal pollen tubes imposes hybridization barriers in flowering plants. Arabidopsis thaliana LURE1 (AtLURE1) peptides and their male receptor PRK6 aid attraction of the growing pollen tube to the ovule. Here, we report that the knockout of the entire AtLURE1 gene family did not affect fertility, indicating that AtLURE1-PRK6–mediated signaling is not required for successful fertilization within one Arabidopsis species. AtLURE1s instead function as pollen tube emergence accelerators that favor conspecific pollen over pollen from other species and thus promote reproductive isolation. We also identified maternal peptides XIUQIU1 to -4, which attract pollen tubes regardless of species. Cooperation between ovule attraction and pollen tube growth acceleration favors conspecific fertilization and promotes reproductive isolation.
Journal Article
Isocitrate lyase plays important roles in plant salt tolerance
Background
Isocitrate lyase (ICL) is a key enzyme in the glyoxylate cycle. In a previous study in rice, the expression of the ICL-encoding gene (
OsICL
) was highly induced by salt stress and its expression was enhanced in transgenic rice lines overexpressing
OsCam1–1
, a calmodulin (CaM)-encoding gene. CaM has been implicated in salt tolerance mechanisms in plants; however, the cellular mechanisms mediated by CaM are not clearly understood. In this study, the role of
OsICL
in plant salt tolerance mechanisms and the possible involvement of CaM were investigated using transgenic plants expressing
OsICL
or
OsCam1–1
.
Results
OsICL
was highly expressed in senesced leaf and significantly induced by salt stress in three
OsCam1–1
overexpressing transgenic rice lines as well as in wild type (WT). In WT young leaf, although
OsICL
expression was not affected by salt stress, all three transgenic lines exhibited highly induced expression levels. In Arabidopsis, salt stress had negative effects on germination and seedling growth of the
AtICL
knockout mutant (
Aticl
mutant). To examine the roles of
OsICL
we generated the following transgenic Arabidopsis lines: the
Aticl
mutant expressing
OsICL
driven by the native
AtICL
promoter, the
Aticl
mutant overexpressing
OsICL
driven by the 35SCaMV promoter, and WT overexpressing
OsICL
driven by the 35SCaMV promoter. Under salt stress, the germination rate and seedling fresh and dry weights of the
OsICL
-expressing lines were higher than those of the
Aticl
mutant, and the two lines with the
icl
mutant background were similar to the WT. The
F
v
/
F
m
and temperature of rosette leaves in the
OsICL
-expressing lines were less affected by salt stress than they were in the
Aticl
mutant. Finally, glucose and fructose contents of the
Aticl
mutant under salt stress were highest, whereas those of
OsICL
-expressing lines were similar to or lower than those of the WT.
Conclusions
OsICL
, a salt-responsive gene, was characterized in the transgenic Arabidopsis lines, revealing that
OsICL
expression could revert the salt sensitivity phenotypes of the
Aticl
knockout mutant. This work provides novel evidence that supports the role of ICL in plant salt tolerance through the glyoxylate cycle and the possible involvement of
OsCam1–1
in regulating its transcription.
Journal Article
Engineered xCas9 and SpCas9‐NG variants broaden PAM recognition sites to generate mutations in Arabidopsis plants
Importantly, we found that SpCas9‐NG could target other types of PAMs, with targeting efficiencies of 3.4% for NGC, 13.0% for NGA and 5.2% for NGT on average, which were higher than these of ZmCas9 and xCas9 3.7 at these target sites (Figure c). [...]we noticed a very high targeting efficiency of SgR‐A3 (NGA PAM) by the SpCas9‐NG variant (i.e. 48.0%), which was comparable to that of wild‐type Cas9 targeting NGG PAMs. [...]our results show that SpCas9‐NG variant can induce indels at non‐NGG sites with higher efficiency than ZmCas9 or xCas9 3.7, but not as efficiently as ZmCas9 for NGG PAM in Arabidopsis. [...]we demonstrated that both the xCas9 3.7 and SpCas9‐NG variants could be used to generate certain mutation types for the candidate genes in Arabidopsis as an alternative to the wild‐type Cas9, especially when the NGG PAMs in these genes are limited. [...]we also found that both xCas9 3.7 and SpCas9‐NG can successfully induce homozygous/biallelic and heterozygous mutations at broad PAM targets once the plants are edited by these systems. [...]we propose that these variants could be used as an alternative to wild‐type Cas9 in Arabidopsis to generate certain types of mutations for candidate genes when NGG PAMs are not available.
Journal Article
The WRKY Transcription Factor WRKY71/EXB1 Controls Shoot Branching by Transcriptionally Regulating RAX Genes in Arabidopsis
Plant shoot branching is pivotal for developmental plasticity and crop yield. The formation of branch meristems is regulated by several key transcription factors including REGULATOR OF AXILLARY MERISTEMS1 (RAX1), RAX2, and RAX3. However, the regulatory network of shoot branching is still largely unknown. Here, we report the identification of EXCESSIVE BRANCHES1 (EXB1), which affects axillary meristem (AM) initiation and bud activity. Overexpression of EXB1 in the gain-of-function mutant exb1-D leads to severe bushy and dwarf phenotypes, which result from excessive AM initiation and elevated bud activities. EXB1 encodes the WRKY transcription factor WRKY71, which has demonstrated transactivation activities. Disruption of WRKY71/EXB1 by chimeric repressor silencing technology leads to fewer branches, indicating that EXB1 plays important roles in the control of shoot branching. We demonstrate that EXB1 controls AM initiation by positively regulating the transcription of RAX1, RAX2, and RAX3. Disruption of the RAX genes partially rescues the branching phenotype caused by EXB1 overexpression. We further show that EXB1 also regulates auxin homeostasis in control of shoot branching. Our data demonstrate that EXB1 plays pivotal roles in shoot branching by regulating both transcription of RAX genes and auxin pathways.
Journal Article