Delayed degradation of chlorophylls and photosynthetic proteins in Arabidopsis autophagy mutants during stress-induced leaf yellowing

Under mild abiotic-stress conditions, Arabidopsis atg mutants showed a functional stay-green phenotype which is probably caused by the lack of chloroplastic autophagy and the retrograde regulation of senescence-associated gene expressio

Regulation of anthocyanin synthesis and embryo quiescence by Viviparous-1 and abscistic acid during maize kernel development

Vita.Abscisic acid (ABA) is required as a co-regulatory factor for all of the regulatory functions associated with Viviparous-1 (Vp1) during maize kernel development. The exception has been anthocyanin synthesis, because carotenoid-deficient viviparous mutants have reduced endogenous ABA but still accumulate anthocyanin pigments. However, if full color kernel blocks are cultured on fluridone medium to reduce endogenous ABA to near zero levels, anthocyanin synthesis is repressed. Addition of exogenous ABA to fluridone medium induces anthocyanin synthesis. Vp1 is expressed in the presence or absence of ABA, but C1 is expressed only when ABA is present. The content of C1 transcripts is increased by adding exogenous ABA into standard medium. When all dominant genes for anthocyanin expression in aleurone tissue are present, the timing and intensity of anthocyanin expression depend on ABA concentration. Both maternal and exogenous ABA are transported into developing maize kernels, and the source of ABA is irrelevant. Genes coding for maize lipase (LIP) and malate synthase (MS) enzymes involved in lipolysis and glyoxylate cycle during germination were cloned to elucidate the Vp1 and ABA regulatory role for the induction of embryo quiescence. The MS and LIP genes are expressed in ABA-insensitive (vp1) and ABA-deficient (vp7, vp10) mutants but not in wild-type embryos at 26 days after pollination (DAP). It appears that Vp1 and ABA regulation is involved in the repression of germination genes at the transcriptional level. This suggests that two major regulatory systems exist for preventing vivipary. The one set of germination genes is down-regulated by ABA alone and the other is by Vp1 and ABA to induce embryo quiescence during maize kernel development. The Vp1 transcription activator regulates the target genes in specific tissue types and then the level of expression is controlled by the concentration of ABA in developing maize kernels

Regulation of anthocyanin synthesis and embryo quiescence by Viviparous-1 and abscistic acid during maize kernel development

Vita.Abscisic acid (ABA) is required as a co-regulatory factor for all of the regulatory functions associated with Viviparous-1 (Vp1) during maize kernel development. The exception has been anthocyanin synthesis, because carotenoid-deficient viviparous mutants have reduced endogenous ABA but still accumulate anthocyanin pigments. However, if full color kernel blocks are cultured on fluridone medium to reduce endogenous ABA to near zero levels, anthocyanin synthesis is repressed. Addition of exogenous ABA to fluridone medium induces anthocyanin synthesis. Vp1 is expressed in the presence or absence of ABA, but C1 is expressed only when ABA is present. The content of C1 transcripts is increased by adding exogenous ABA into standard medium. When all dominant genes for anthocyanin expression in aleurone tissue are present, the timing and intensity of anthocyanin expression depend on ABA concentration. Both maternal and exogenous ABA are transported into developing maize kernels, and the source of ABA is irrelevant. Genes coding for maize lipase (LIP) and malate synthase (MS) enzymes involved in lipolysis and glyoxylate cycle during germination were cloned to elucidate the Vp1 and ABA regulatory role for the induction of embryo quiescence. The MS and LIP genes are expressed in ABA-insensitive (vp1) and ABA-deficient (vp7, vp10) mutants but not in wild-type embryos at 26 days after pollination (DAP). It appears that Vp1 and ABA regulation is involved in the repression of germination genes at the transcriptional level. This suggests that two major regulatory systems exist for preventing vivipary. The one set of germination genes is down-regulated by ABA alone and the other is by Vp1 and ABA to induce embryo quiescence during maize kernel development. The Vp1 transcription activator regulates the target genes in specific tissue types and then the level of expression is controlled by the concentration of ABA in developing maize kernels

Quantitative Trait Locus Mapping and Candidate Gene Analysis for Functional Stay-Green Trait in Rice

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Functional stay-green (FSG) delays leaf yellowing, maintaining photosynthetic competence, whereas nonfunctional stay-green (NFSG) retains only leaf greenness without sustaining photosynthetic activity. Retention of chlorophylls and photosynthetic capacity is important for increasing crop yield. We determined the main-effect quantitative trait loci (QTLs) for FSG traits in the japonica rice SNU-SG1 and isolated candidate genes. To identify QTLs influencing FSG, we analyzed eight traits: (1) 1 day after heading-degree of chlorophyll content of flag leaf, (2) 1 day after heading-degree of chlorophyll content of second leaf, (3) 1 day after heading-degree of chlorophyll content of flag and second leaves, (4) 50 day after heading-degree of chlorophyll content of flag leaf, (5) 50 day after heading-degree of chlorophyll content of second leaf, (6) 50 day after heading-degree of chlorophyll content of flag and second leaves, (7) relative decline degree of chlorophyll content of flag and second leaves, and (8) flowering time. We carried out QTL analysis with F7 RIL from a cross of japonica rice SNU-SG1 and indica rice Milyang23 (M23). Using 131 molecular markers, we identified 18 QTLs for the eight traits with a threshold LOD value > 2.8. Sequence analysis identified 16 candidate genes for 10 main-effect QTLs. Of these, we have chosen seven strong candidate genes for the 10 main-effect QTLs. These genetic resources will be useful for breeding high-yielding rice cultivars.OAIID:oai:osos.snu.ac.kr:snu2015-01/102/0000003606/7ADJUST_YN:YEMP_ID:A002118DEPT_CD:517CITE_RATE:0FILENAME:2015-7 fsg (plant breed biotechnol)-임정현.pdfDEPT_NM:식물생산과학부SCOPUS_YN:NCONFIRM:

Gibberellic Acid: A Key Phytohormone for Spikelet Fertility in Rice Grain Production

The phytohormone gibberellic acid (GA) has essential signaling functions in multiple processes during plant development. In the “Green Revolution”, breeders developed high-yield rice cultivars that exhibited both semi-dwarfism and altered GA responses, thus improving grain production. Most studies of GA have concentrated on germination and cell elongation, but GA also has a pivotal role in floral organ development, particularly in stamen/anther formation. In rice, GA signaling plays an important role in spikelet fertility; however, the molecular genetic and biochemical mechanisms of GA in male fertility remain largely unknown. Here, we review recent progress in understanding the network of GA signaling and its connection with spikelet fertility, which is tightly associated with grain productivity in cereal crops

The Divergent Roles of STAYGREEN (SGR) Homologs in Chlorophyll Degradation

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/.Degradation of chlorophyll (Chl) by Chl catabolic enzymes (CCEs) causes the loss of green color that typically occurs during senescence of leaves. In addition to CCEs, STAYGREEN1 (SGR1) functions as a key regulator of Chl degradation. Although sgr1 mutants in many plant species exhibit a staygreen phenotype, the biochemical function of the SGR1 protein remains elusive. Many recent studies have examined the physiological and molecular roles of SGR1 and its homologs (SGR2 and SGR-LIKE) in Chl metabolism, finding that these proteins have different roles in different species. In this review, we summarize the recent studies on SGR and discuss the most likely functions of SGR homologs.OAIID:oai:osos.snu.ac.kr:snu2015-01/102/0000003606/4ADJUST_YN:YEMP_ID:A002118DEPT_CD:517CITE_RATE:2.09FILENAME:2015-4 sgr minireview (mol cells).pdfDEPT_NM:식물생산과학부SCOPUS_YN:YCONFIRM:

The Rice Rolled Fine Striped (RFS) CHD3/Mi-2 Chromatin Remodeling Factor Epigenetically Regulates Genes Involved in Oxidative Stress Responses During Leaf Development

In rice (Oryza sativa), moderate leaf rolling increases photosynthetic competence and raises grain yield; therefore, this important agronomic trait has attracted much attention from plant biologists and breeders. However, the relevant molecular mechanism remains unclear. Here, we isolated and characterized Rolled Fine Striped (RFS), a key gene affecting rice leaf rolling, chloroplast development, and reactive oxygen species (ROS) scavenging. The rfs-1 gamma-ray allele and the rfs-2 T-DNA insertion allele of RFS failed to complement each other and their mutants had similar phenotypes, producing extremely incurved leaves due to defective development of vascular cells on the adaxial side. Map-based cloning showed that the rfs-1 mutant harbors a 9-bp deletion in a gene encoding a predicted CHD3/Mi-2 chromatin remodeling factor belonging to the SNF2-ATP-dependent chromatin remodeling family. RFS was expressed in various tissues and accumulated mainly in the vascular cells throughout leaf development. Furthermore, RFS deficiency resulted in a cell death phenotype that was caused by ROS accumulation in developing leaves. We found that expression of five ROS-scavenging genes [encoding catalase C, ascorbate peroxidase 8, a putative copper/zinc superoxide dismutase (SOD), a putative SOD, and peroxiredoxin IIE2] decreased in rfs-2 mutants. Western-blot and chromatin immunoprecipitation (ChIP) assays demonstrated that rfs-2 mutants have reduced H3K4me3 levels in ROS-related genes. Loss-of-function in RFS also led to multiple developmental defects, affecting pollen development, grain filling, and root development. Our results suggest that RFS is required for many aspects of plant development and its function is closely associated with epigenetic regulation of genes that modulate ROS homeostasis