Circadian clocks regulate growth and development in plants and animals, but the role of circadian regulation in crop production is poorly understood. Rice (
) grain yield is largely determined by ...tillering, which is mediated by physiological and genetic factors. Here we report a regulatory loop that involves the circadian clock, sugar, and strigolactone (SL) pathway to regulate rice tiller-bud and panicle development. Rice
(
) positively regulates expression of
(
, also known as
),
(
), and
(
, also known as
) to repress tiller-bud outgrowth. Downregulating and overexpressing
increases and reduces tiller numbers, respectively, whereas manipulating
(
) expression results in the opposite effects.
also regulates
expression to mediate panicle and grain development. Genetic analyses using double mutants and overexpression in the mutants show that
,
, and
act downstream of
Sugars repress
expression in roots and tiller buds to promote tiller-bud outgrowth. The circadian clock integrates sugar responses and the SL pathway to regulate tiller and panicle development, providing insights into improving plant architecture and yield in rice and other cereal crops.
Strigolactones （SLs）, a group of carotenoid derived terpenoid lactones, are root-to-shoot phytohormones sup- pressing shoot branching by inhibiting the outgrowth of axillary buds. DWARF 53 （D53）, the ...key repressor of the SL signaling pathway, is speculated to regulate the downstream transcriptional network of the SL response. However, no downstream transcription factor targeted by D53 has yet been reported. Here we report that Ideal Plant Architecture 1 （IPA1）, a key regulator of the plant architecture in rice, functions as a direct downstream component of D53 in reg- ulating tiller number and SL-induced gene expression. We showed that D53 interacts with IPA1 in vivo and in vitro and suppresses the transcriptional activation activity of IPA1. We further showed that IPA1 could directly bind to the D53 promoter and plays a critical role in the feedback regulation of SL-induced D53 expression. These findings re- veal that IPA1 is likely one of the long-speculated transcription factors that act with D53 to mediate the SL-regulated tiller development in rice.
Dear Editor Rice （Oryza sativa L.） is one of the world＇s most important staple crops and a powerful model system for studying monocot spe- cies because of its relatively small genome, rich genomic ...re- sources, and a highly efficient transformation system. With the completion of rice genome sequencing, the challenge of the post-genomic era is to systematically analyze the functions of all rice genes. Gene knockout is a frequently used and effective strategy for achieving this goal. Thus, generation of large-scale mutants at the whole-genome level is of great value for both func- tional genomics and genetic improvement of rice. Traditionally,
Summary
Cucumber mosaic virus suppressor 2b (CMV2b) is a nuclear viral suppressor that interferes with local and systemic silencing and inhibits AGO1 slicer activity. CMV2b‐mediated transgene ...hypomethylation and its localization in Cajal bodies suggests a role of CMV2b in RNA‐directed DNA methylation (RdDM). However, its direct involvement in RdDM, or its binding with small RNAs (sRNAs) in vivo is not yet established. Here, we show that CMV2b binds both microRNAs (miRNAs) and small interfering RNAs (siRNAs) in vivo. sRNA sequencing data from the CMV2b immunocomplex revealed its preferential binding with 24‐nt repeat‐associated siRNAs. We provide evidence that CMV2b also has direct interaction with the AGO4 protein by recognizing its PAZ and PIWI domains. Subsequent analysis of AGO4 functions revealed that CMV2b reduced AGO4 slicer activity and the methylation of several loci, accompanied by the augmented accumulation of 24‐nt siRNAs in Arabidopsis inflorescences. Intriguingly, CMV2b also regulated an AGO4‐related epiallele independently of its catalytic potential, which further reinforces the repressive effects of CMV2b on AGO4 activity. Collectively, our results demonstrate that CMV2b can counteract AGO4‐related functions. We propose that by adopting novel counter‐host defense strategies against AGO1 and AGO4 proteins, CMV creates a favorable cellular niche for its proliferation.
RNA silencing is an important mechanism for regulation of endogenous gene expression and defense against genomic intruders in plants. This natural defense system was adopted to generate ...virus-resistant plants even before the mechanism of RNA silencing was unveiled. With the clarification of that mechanism, transgenic antiviral plants were developed that expressed artificial virus-specific hairpin RNAs (hpRNAs) or microRNAs (amiRNAs) in host plants. Previous works also showed that plant-mediated RNA silencing technology could be a practical method for constructing insect-resistant plants by expressing hpRNAs targeting essential genes of insects.
In this study, we chose aphid Myzus persicae of order Hemiptera as a target insect. To screen for aphid genes vulnerable to attack by plant-mediated RNA silencing to establish plant aphid resistance, we selected nine genes of M. persicae as silencing targets, and constructed their hpRNA-expressing vectors. For the acetylcholinesterase 2 coding gene (MpAChE2), two amiRNA-expressing vectors were also constructed. The vectors were transformed into tobacco plants (Nicotiana tabacum cv. Xanti). Insect challenge assays showed that most of the transgenic plants gained aphid resistance, among which those expressing hpRNAs targeting V-type proton ATPase subunit E-like (V-ATPaseE) or tubulin folding cofactor D (TBCD) genes displayed stronger aphicidal activity. The transgenic plants expressing amiRNAs targeting two different sites in the MpAChE2 gene exhibited better aphid resistance than the plants expressing MpAChE2-specific hpRNA.
Our results indicated that plant-mediated insect-RNA silencing might be an effective way to develop plants resistant to insects with piercing-sucking mouthparts, and both the selection of vulnerable target genes and the biogenetic type of the small RNAs were crucial for the effectiveness of aphid control. The expression of insect-specific amiRNA is a promising and preferable approach to engineer plants resistant to aphids and, possibly, to other plant-infesting insects.
The P6 protein of Rice yellow stunt rhabdovirus (RYSV) is a virion structural protein that can be phosphorylated in vitro. However its exact function remains elusive. We found that P6 enhanced the ...virulence of Potato virus X (PVX) in Nicotiana benthamiana and N. tabacum plants, suggesting that it might function as a suppressor of RNA silencing. We examined the mechanism of P6-mediated silencing suppression by transiently expressing P6 in both N. benthamiana leaves and rice protoplasts. Our results showed that P6 could repress the production of secondary siRNAs and inhibit systemic green fluorescent protein RNA silencing but did not interfere with local RNA silencing in N. benthamiana plants or in rice protoplasts. Intriguingly, P6 and RDR6 had overlapping subcellular localization and P6 bound both rice and Arabidopsis RDR6 in vivo. Furthermore, transgenic rice plants expressing P6 showed enhanced susceptibility to infection by Rice stripe virus. Hence, we propose that P6 is part of the RYSV's counter-defense machinery against the plant RNA silencing system and plays a role mainly in affecting RDR6-mediated secondary siRNA synthesis. Our work provides a new perspective on how a plant-infecting nucleorhabdovirus may counteract host RNA silencing-mediated antiviral defense.
SRWD1, a member of the WD40 protein subfamily, is induced by salt stress in rice and its homolog in barley can bind to GAMYB, implying that SRWD1 might be involved in plant defense against ...environmental stress and gibberellic acid(GA) signalings. In this study, we focused on the biological functions and regulation mechanisms of SRWD1 in rice. The results showed that SRWD1 expression was repressed by GA and induced by abscisic acid(ABA). Two WRKY-family transcription factors, Os WRKY45 and Os WRKY72, were found to regulate SRWD1 expression by directly binding to the W-box region in its promoter. Transient co-expression and yeast two-hybrid analyses showed that a DELLA protein strengthened the activation of Os WRKY45 and partly relieved the suppression of Os WRKY72 by binding to them.Interestingly, both SRWD1-overexpressing transgenic plants and SRWD1-knockout mutants showed dwarf phenotypes and resistance to Xanthomonas oryzae.
This paper presents the research on fracture failure analysis and failure criterion for PTFE-coated woven fabrics. First, groups of on-axial and off-axial tensile tests are carried out, and the ...corresponding failure mechanisms are analyzed. Then, the samples with initial defects are tested and the fracture toughness is discussed. Finally, several current strength criteria are compared to predict the failure strength of PTFE-coated woven fabrics and a new strength criterion is proposed. Results show the material failure strength depends on the stress ratio and off-axial angle of sample. The ratio of principal stress decides the material strength, and the angle between the principal stress and yarn orientation decides the failure mode. The predictions of current strength criteria agree well with most of the experiment data, except for the samples of small off-axial angles. The disagreements could be attributed to the unbalanced woven structure due primarily to the crimp interchange in the weaving and coating processes. The new strength criterion can make a good prediction of the failure strength of PTFE-coated woven fabrics.
Abstract
Chilling is a major abiotic stress harming rice development and productivity. The C-REPEAT BINDING FACTOR (CBF)-dependent transcriptional regulatory pathway plays a central role in cold ...stress and acclimation in
Arabidopsis
. In rice, several genes have been reported in conferring chilling tolerance, however, the chilling signaling in rice remains largely unknown. Here, we report the chilling-induced OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 6 (OsSAPK6)-IDEAL PLANT ARCHITECTURE 1 (IPA1)-OsCBF3 signal pathway in rice. Under chilling stress, OsSAPK6 could phosphorylate IPA1 and increase its stability. In turn, IPA1 could directly bind to the GTAC motif on the
OsCBF3
promoter to elevate its expression. Genetic evidence showed that OsSAPK6, IPA1 and OsCBF3 were all positive regulators of rice chilling tolerance. The function of OsSAPK6 in chilling tolerance depended on IPA1, and overexpression of
OsCBF3
could rescue the chilling-sensitive phenotype of
ipa1
loss-of-function mutant. Moreover, the natural gain-of-function allele
ipa1-2D
could simultaneously enhance seedling chilling tolerance and increase grain yield. Taken together, our results revealed a chilling-induced OsSAPK6-IPA1-OsCBF signal cascade in rice, which shed new lights on chilling stress-tolerant rice breeding.
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