Dev Cell , IF:10.092 , 2020 Dec doi: 10.1016/j.devcel.2020.12.001
A BIN2-GLK1 Signaling Module Integrates Brassinosteroid and Light Signaling to Repress Chloroplast Development in the Dark.
Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Sciences, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, P.R.China. Electronic address: zhdawei@scu.edu.cn.; Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Sciences, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, P.R.China.; Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA.; School of Life Science, Guangzhou University, Guangzhou, P.R.China.; Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Sciences, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, P.R.China. Electronic address: hhlin@scu.edu.cn.
Arabidopsis GLYCOGEN SYNTHASE KINASE 3 (GSK3)-like kinases play various roles in plant development, including chloroplast development, but the underlying molecular mechanism is not well defined. Here, we demonstrate that transcription factors GLK1 and GLK2 interact with and are phosphorylated by the BRASSINOSTEROID insensitive2 (BIN2). The loss-of-function mutant of BIN2 and its homologs, bin2-3 bil1 bil2, displays abnormal chloroplast development, whereas the gain-of-function mutant, bin2-1, exhibits insensitivity to BR-induced de-greening and reduced numbers of thylakoids per granum, suggesting that BIN2 positively regulates chloroplast development. Furthermore, BIN2 phosphorylates GLK1 at T175, T238, T248, and T256, and mutations of these phosphorylation sites alter GLK1 protein stability and DNA binding and impair plant responses to BRs/darkness. On the other hand, BRs and darkness repress the BIN2-GLK module to enhance BR/dark-mediated de-greening and impair the formation of the photosynthetic apparatus. Our results thus provide a mechanism by which BRs modulate photomorphogenesis and chloroplast development.
PMID: 33357403
Plant J , IF:6.141 , 2020 Dec doi: 10.1111/tpj.15112
Phytohormones in Fruit Development and Maturation.
Section of Plant Breeding and Genetics, School of Integrative Plant Sciences, Cornell University, Ithaca, NY, 14853, USA.; United States Department of Agriculture - Agricultural Research Service and Boyce Thompson Institute for Plant Research, Cornell University campus, Ithaca, NY, 14853, USA.
Phytohormones are integral to the regulation of fruit development and maturation. This review expands upon current understanding of the relationship between hormone signaling and fruit development, emphasizing fleshy fruit and highlighting recent work in the model crop tomato and additional species. Fruit development comprises fruit set initiation, growth, and maturation and ripening. Fruit set transpires after fertilization and is associated with auxin and gibberellic acid (GA) signaling. Interaction between auxin and GAs, as well as other phytohormones, is mediated by auxin-responsive Aux/IAA and ARF proteins. Fruit growth consists of cell division and expansion, the former shown to be influenced by auxin signaling. While regulation of cell expansion is less thoroughly understood, evidence indicates synergistic regulation via both auxin and GAs, with input from additional hormones. Fruit maturation, a transitional phase that precipitates ripening, occurs when auxin and GA levels subside with a concurrent rise in abscisic acid (ABA) and ethylene. During fruit ripening, ethylene plays a clear role in climacteric fruits, whereas non-climacteric ripening is generally associated with ABA. Recent evidence indicates varying requirements for both hormones within both ripening physiologies, suggesting rebalancing and specification of roles for common regulators rather than reliance upon one. Numerous recent discoveries pertaining to the molecular basis of hormonal activity and cross-talk are discussed, while we also note that many questions remain such as the molecular basis of additional hormonal activities, the role of epigenome changes and how prior discoveries translate to the plethora of angiosperm species.
PMID: 33274492
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa592
The APETALA2 transcription factor LsAP2 regulates seed shape in lettuce.
Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, College of Horticulture, China Agricultural University, Beijing, China.
Seeds are major vehicles of propagation and dispersal in plants. A number of transcription factors, including APETALA2 (AP2), play crucial roles during the seed development process in various plant species. However, genes essential for seed development and the regulatory networks during seed development remain unclear in lettuce. Here, we identified a lettuce AP2 (LsAP2) gene that was highly expressed at the early stages of seed development. LsAP2 knockout plants obtained by the CRISPR/Cas9 system were used to explore the biological function of LsAP2. Compared with wild-type, the seeds of the Lsap2 mutant plants had increased length and decreased width, and developed an extended tip at the seed top. After further investigating the seed structural characteristics of Lsap2 mutant plants, we proposed a new function of LsAP2 in seed dispersal. Moreover, we identified several interactors of LsAP2. Our results showed that LsAP2 directly interacted with the lettuce homolog of BREVIPEDICELLUS (LsBP) and promoted the expression of LsBP. Transcriptome analysis revealed that LsAP2 might also be involved in brassinosteroid biosynthesis and signaling pathways. Taken together, our data indicate that LsAP2 has a significant function in regulating seed shape in lettuce.
PMID: 33340036
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa565
ZmCLA4 regulates leaf angle through multiple hormone signaling pathways in maize.
College of Agronomy, Synergetic Innovation Center of Henan Grain Crops and National Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Longzihu University Park, Zhengdong New Area, Zhengzhou, Henan, China.; Henan Academy of Agricultural Science, Zhengzhou, Henan, China.
Leaf angle (LA) is an important agronomic trait in cereals that shares a close relationship with crop architecture and grain yield. Although it has been previously reported that ZmCLA4 can influence LA, the underlying mechanism of it remains unclear. In this study, we used Gal4-LexA/UAS system and transactivation analysis to demonstrate that ZmCLA4 is a transcriptional repressor that regulates LA. DNA affinity purification sequencing (DAP-Seq) analysis revealed that ZmCLA4 mainly binds to the promoters containing the EAR motif (CACCGGAC) as well as two motifs (CCGARGS and CDTCNTC) to inhibit the expression of its target genes. Further analysis of ZmCLA4 target genes indicated that ZmCLA4 functions as a hub of multiple plant hormone signaling pathways because ZmCLA4 was found to directly bind to the promoters of multiple genes including ZmARF22 and ZmIAA26 in the auxin transport pathway, ZmBZR3 in the brassinosteroid signaling pathway, two ZmWRKY genes involved in abscisic acid metabolism, ZmCYP genes (ZmCYP75B1, ZmCYP93D1) related to jasmonic acid metabolism, and ZmABI3 involved in the ethylene response pathway. Overall, our work provides deep insights into the regulatory network of ZmCLA4 in controlling LA in maize.
PMID: 33270106
Development , IF:5.611 , 2020 Dec , V147 (24) doi: 10.1242/dev.196618
Asynchrony of ovule primordia initiation in Arabidopsis.
Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai 200240, China.; Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo, Zhejiang 315211, China.; State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, Beijing 100101, China.; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.; National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.; Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai 200240, China whlin@sjtu.edu.cn.
Plant ovule initiation determines the maximum of ovule number and has a great impact on the seed number per fruit. The detailed processes of ovule initiation have not been accurately described, although two connected processes, gynoecium and ovule development, have been investigated. Here, we report that ovules initiate asynchronously. The first group of ovule primordia grows out, the placenta elongates, the boundaries of existing ovules enlarge and a new group of primordia initiates from the boundaries. The expression pattern of different marker genes during ovule development illustrates that this asynchronicity continues throughout whole ovule development. PIN-FORMED1 polar distribution and auxin response maxima correlate with ovule primordia asynchronous initiation. We have established computational modeling to show how auxin dynamics influence ovule primordia initiation. Brassinosteroid signaling positively regulates ovule number by promoting placentae size and ovule primordia initiation through strengthening auxin response. Transcriptomic analysis demonstrates numerous known regulators of ovule development and hormone signaling, and many new genes are identified that are involved in ovule development. Taken together, our results illustrate that the ovule primordia initiate asynchronously and the hormone signals are involved in the asynchrony.
PMID: 33234714
Int J Mol Sci , IF:4.556 , 2020 Dec , V21 (24) doi: 10.3390/ijms21249666
Functional Characterization of BRASSINAZOLE-RESISTANT 1 in Panax Ginseng (PgBZR1) and Brassinosteroid Response during Storage Root Formation.
Department of Biology, College of Natural Sciences, Chungbuk National University, Cheongju 28644, Korea.; Department of Forest Science, College of Agriculture, Life & Environmental Sciences, Chungbuk National University, Cheongju 28644, Korea.; Department of Industrial Plant Science & Technology, College of Agriculture, Life & Environmental Sciences, Chungbuk National University, Cheongju 28644, Korea.
Brassinosteroids (BRs) play crucial roles in the physiology and development of plants. In the model plant Arabidopsis, BR signaling is initiated at the level of membrane receptors, BRASSINOSTEROIDS INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) complex, thus activating the transcription factors (TFs) BRASSINAZOLE RESISTANT 1/BRI1-EMS-SUPPRESSOR 1 (BZR1/BES1) to coordinate BR responsive genes. BRASSINOSTEROIDS INSENSITIVE 2 (BIN2), glycogen synthase kinase 3 (GSK3) like-kinase, negatively regulates BZR1/BES1 transcriptional activity through phosphorylation-dependent cytosolic retention and shuttling. However, it is still unknown whether this mechanism is conserved in Panax ginseng C. A. Mayer, a member of the Araliaceae family, which is a shade-tolerant perennial root crop. Despite its pharmacological and agricultural importance, the role of BR signaling in the development of P. ginseng and characterization of BR signaling components are still elusive. In this study, by utilizing the Arabidopsisbri1 mutant, we found that ectopic expression of the gain of function form of PgBZR1 (Pgbzr1-1D) restores BR deficiency. In detail, ectopic expression of Pgbzr1-1D rescues dwarfism, defects of floral organ development, and hypocotyl elongation of bri1-5, implying the functional conservation of PgBZR1 in P. ginseng. Interestingly, brassinolide (BL) and BRs biosynthesis inhibitor treatment in two-year-old P. ginseng storage root interferes with and promotes, respectively, secondary growth in terms of xylem formation. Altogether, our results provide new insight into the functional conservation and potential diversification of BR signaling and response in P. ginseng.
PMID: 33352948
Front Plant Sci , IF:4.402 , 2020 , V11 : P621859 doi: 10.3389/fpls.2020.621859
Regulation of Brassinosteroid Signaling and Salt Resistance by SERK2 and Potential Utilization for Crop Improvement in Rice.
National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, China.
The complex roles of the steroid hormone brassinosteroids (BRs) in many different yield- and stress-related traits make it difficult to utilize the hormones for crop improvement. Here, we show that SERK2 as a BR signaling component is a potentially useful candidate for BR manipulation in rice. We generated multiple mutant alleles of SERK2 by CRISPR/Cas9 editing and show that knockout of SERK2 results in a compact structure accompanied with increased grain size. SERK2 is localized on plasma membrane and can interact with OsBRI1, the BR receptor, suggesting its conserved role as co-receptor in BR signaling. Consistently, the mutant has impaired BR sensitivity compared to wild type. Notably, the mutant is highly sensitive to salt stress as evaluated by plant survival rate as well as transcriptome analysis, whereas has slightly increased sensitivity to ABA, the stress hormone. By contrast, overexpression of SERK2 significantly enhances grain size and salt stress resistance, importantly, without affecting plant architecture. Furthermore, while salt suppresses SERK2 transcription, the protein is greatly induced by salt stress. Taken together, we propose that the adverse condition induces SERK2 accumulation to enhance early BR signaling on plasma membrane in favor of the anti-stress response. Our results illustrate the great potentials of specific BR components such as SERK2 for crop improvement by utilizing flexible strategies.
PMID: 33362843
Front Plant Sci , IF:4.402 , 2020 , V11 : P617162 doi: 10.3389/fpls.2020.617162
Updates on BES1/BZR1 Regulatory Networks Coordinating Plant Growth and Stress Responses.
Department of Genetics, Development and Cell Biology, Plant Sciences Institute, Iowa State University, Ames, IA, United States.
Brassinosteroids (BRs) play pivotal roles in the regulation of many dimensions of a plant's life. Hence, through extensive efforts from many research groups, BR signaling has emerged as one of the best-characterized plant signaling pathways. The key molecular players of BR signaling from the cell surface to the nucleus important for the regulation of plant growth and development are well-established. Recent data show that BRs also modulate plant responses to environmental stresses such as drought and pathogen infection. In this mini review, we present the recent progress in BR signaling specifically in the post-translational SUMO modification of BR's master regulators, BES1/BZR1. We also discuss recent findings on the crosstalk between BR, UV light, and jasmonic acid signaling pathways to balance growth during light stress and pathogen infections. Finally, we describe the current update on the molecular link between BR signaling and intracellular auxin transport that essential for plant development.
PMID: 33343611
Front Genet , IF:3.258 , 2020 , V11 : P584678 doi: 10.3389/fgene.2020.584678
Gene Expression Dynamics in Rice Peduncles at the Heading Stage.
Grass Genetics and Informatics Group, School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.; Division of Plant Physiology, ICAR-Indian Agricultural Research Institute, New Delhi, India.; School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.; Grass Genetics and Informatics Group, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.
Improving grain yield in the staple food crop rice has been long sought goal of plant biotechnology. One of the traits with significant impact on rice breeding programs is peduncle elongation at the time of heading failing which leads to significant reduction in grain yield due to incomplete panicle exsertion. To decipher transcriptional dynamics and molecular players underlying peduncle elongation, we performed RNA sequencing analysis of elongating and non-elongating peduncles in two Indian cultivars, Swarna and Pokkali, at the time of heading. Along with genes associated with cell division and cell wall biosynthesis, we observed significant enrichment of genes associated with auxins, gibberellins, and brassinosteroid biosynthesis/signaling in the elongating peduncles before heading in both the genotypes. Similarly, genes associated with carbohydrate metabolism and mobilization, abiotic stress response along with cytokinin, abscisic acid, jasmonic acid, and ethylene biosynthesis/signaling were enriched in non-elongating peduncles post heading. Significant enrichment of genes belonging to key transcription factor families highlights their specialized roles in peduncle elongation and grain filling before and after heading, respectively. A comparison with anther/pollen development-related genes provided 76 candidates with overlapping roles in anther/pollen development and peduncle elongation. Some of these are important for carbohydrate remobilization to the developing grains. These can be engineered to combat with incomplete panicle exsertion in male sterile lines and manipulate carbohydrate dynamics in grasses. Overall, this study provides baseline information about potential target genes for engineering peduncle elongation with implications on plant height, biomass composition and grain yields in rice.
PMID: 33343630
Plants (Basel) , IF:2.762 , 2020 Dec , V9 (12) doi: 10.3390/plants9121751
Identification of Cis-Regulatory Sequences Controlling Pollen-Specific Expression of Hydroxyproline-Rich Glycoprotein Genes in Arabidopsis thaliana.
School of Electrical Engineering and Computer Science, Russ College of Engineering, Ohio University, Athens, OH 45701, USA.; Department of Environmental and Plant Biology, Molecular and Cellular Biology Program, College of Arts and Sciences, Ohio University, Athens, OH 45701, USA.
Hydroxyproline-rich glycoproteins (HRGPs) are a superfamily of plant cell wall structural proteins that function in various aspects of plant growth and development, including pollen tube growth. We have previously characterized protein sequence signatures for three family members in the HRGP superfamily: the hyperglycosylated arabinogalactan-proteins (AGPs), the moderately glycosylated extensins (EXTs), and the lightly glycosylated proline-rich proteins (PRPs). However, the mechanism of pollen-specific HRGP gene expression remains unexplored. To this end, we developed an integrative analysis pipeline combining RNA-seq gene expression and promoter sequences to identify cis-regulatory motifs responsible for pollen-specific expression of HRGP genes in Arabidopsis thaliana. Specifically, we mined the public RNA-seq datasets and identified 13 pollen-specific HRGP genes. Ensemble motif discovery identified 15 conserved promoter elements between A.thaliana and A. lyrata. Motif scanning revealed two pollen related transcription factors: GATA12 and brassinosteroid (BR) signaling pathway regulator BZR1. Finally, we performed a regression analysis and demonstrated that the 15 motifs provided a good model of HRGP gene expression in pollen (R = 0.61). In conclusion, we performed the first integrative analysis of cis-regulatory motifs in pollen-specific HRGP genes, revealing important insights into transcriptional regulation in pollen tissue.
PMID: 33322028
Plant Signal Behav , IF:1.671 , 2020 Dec : P1855845 doi: 10.1080/15592324.2020.1855845
ShHTL7 requires functional brassinosteroid signaling to initiate GA-independent germination.
Department of Cell & Systems Biology, University of Toronto , Toronto, Canada.
In the model plant Arabidopsis thaliana, two mutually antagonistic hormones regulate germination: abscisic acid (ABA) which promotes dormancy and gibberellins (GA) which breaks dormancy. Mutants auxotrophic for or insensitive to GA do not germinate. However, changes in the signaling flux through other hormone pathways will permit GA-independent germination. These changes include increased brassinosteroid (BR) signaling and decreased ABA signaling. Recently, strigolactone (SL) was also shown to enable GA-independent germination, provided the seeds express the SL receptor ShHTL7 from the parasitic plant Striga hermonthica. Here we show that a mutation which reduces sensitivity to BR (bri1-6) prevents ShHTL7 from promoting GA-independent germination. Further, we show that neither ShHTL7 nor the constitutive karrikin signaling mutant smax1-2 confer insensitivity to ABA. These results suggest ShHTL7 requires functional BR perception to bypass the GA requirement for germination.
PMID: 33300428