TY - JOUR A1 - Nakamura, Yasunori A1 - Ono, Masami A1 - Utsumi, Chikako A1 - Steup, Martin T1 - Functional interaction between plastidial starch phosphorylase and starch branching enzymes from rice during the synthesis of branched maltodextrins JF - Plant & cell physiology N2 - The present study established the way in which plastidial alpha-glucan phosphorylase (Pho1) synthesizes maltodextrin (MD) which can be the primer for starch biosynthesis in rice endosperm. The synthesis of MD by Pho1 was markedly accelerated by branching enzyme (BE) isozymes, although the greatest effect was exhibited by the presence of branching isozyme I (BEI) rather than by isozyme IIa (BEIIa) or isozyme IIb (BEIIb). The enhancement of the activity of Pho1 by BE was not merely due to the supply of a non-reducing ends. At the same time, Pho1 greatly enhanced the BE activity, possibly by generating a branched carbohydrate substrate which is used by BE with a higher affinity. The addition of isoamylase to the reaction mixture did not prevent the concerted action of Pho1 and BEI. Furthermore, in the product, the branched structure was, at least to some extent, maintained. Based on these results we propose that the interaction between Pho1 and BE is not merely due to chain-elongating and chain-branching reactions, but occurs in a physically and catalytically synergistic manner by each activating the mutual capacity of the other, presumably forming a physical association of Pho1, BEI and branched MDs. This close interaction might play a crucial role in the synthesis of branched MDs and the branched MDs can act as a primer for the biosynthesis of amylopectin molecules. KW - Amylopectin KW - Glucan KW - Phosphorylase KW - Rice KW - Starch KW - Starch branching enzyme Y1 - 2012 U6 - https://doi.org/10.1093/pcp/pcs030 SN - 0032-0781 VL - 53 IS - 5 SP - 869 EP - 878 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Zhao, Liming A1 - Xia, Yan A1 - Wu, Xiao-Yuan A1 - Schippers, Jos H. M. A1 - Jing, Hai-Chun T1 - Phenotypic analysis and molecular markers of leaf senescence JF - Plant Senescence: Methods and Protocols N2 - The process of leaf senescence consists of the final stage of leaf development. It has evolved as a mechanism to degrade macromolecules and micronutrients and remobilize them to other developing parts of the plant; hence it plays a central role for the survival of plants and crop production. During senescence, a range of physiological, morphological, cellular, and molecular events occur, which are generally referred to as the senescence syndrome that includes several hallmarks such as visible yellowing, loss of chlorophyll and water content, increase of ion leakage and cell death, deformation of chloroplast and cell structure, as well as the upregulation of thousands of so-called senescence-associated genes (SAGs) and downregulation of photosynthesis-associated genes (PAGs). This chapter is devoted to methods characterizing the onset and progression of leaf senescence at the morphological, physiological, cellular, and molecular levels. Leaf senescence normally progresses in an age-dependent manner but is also induced prematurely by a variety of environmental stresses in plants. Focused on the hallmarks of the senescence syndrome, a series of protocols is described to asses quantitatively the senescence process caused by developmental cues or environmental perturbations. We first briefly describe the senescence process, the events associated with the senescence syndrome, and the theories and methods to phenotype senescence. Detailed protocols for monitoring senescence in planta and in vitro, using the whole plant and the detached leaf, respectively, are presented. For convenience, most of the protocols use the model plant species Arabidopsis and rice, but they can be easily extended to other plants. KW - Leaf senescence KW - Visible yellowing KW - Chlorophyll KW - Ion leakage KW - Cell death KW - Senescence-associated genes (SAGs) KW - Arabidopsis KW - Rice Y1 - 2018 SN - 978-1-4939-7672-0 SN - 978-1-4939-7670-6 U6 - https://doi.org/10.1007/978-1-4939-7672-0_3 SN - 1064-3745 SN - 1940-6029 VL - 1744 SP - 35 EP - 48 PB - Humana Press Inc. CY - Totowa ER - TY - JOUR A1 - Sharma, Niharika A1 - Dang, Trang Minh A1 - Singh, Namrata A1 - Ruzicic, Slobodan A1 - Müller-Röber, Bernd A1 - Baumann, Ute A1 - Heuer, Sigrid T1 - Allelic variants of OsSUB1A cause differential expression of transcription factor genes in response to submergence in rice JF - Rice N2 - Background: Flooding during seasonal monsoons affects millions of hectares of rice-cultivated areas across Asia. Submerged rice plants die within a week due to lack of oxygen, light and excessive elongation growth to escape the water. Submergence tolerance was first reported in an aus-type rice landrace, FR13A, and the ethylene-responsive transcription factor (TF) gene SUB1A-1 was identified as the major tolerance gene. Intolerant rice varieties generally lack the SUB1A gene but some intermediate tolerant varieties, such as IR64, carry the allelic variant SUB1A-2. Differential effects of the two alleles have so far not been addressed. As a first step, we have therefore quantified and compared the expression of nearly 2500 rice TF genes between IR64 and its derived tolerant near isogenic line IR64-Sub1, which carries the SUB1A-1 allele. Gene expression was studied in internodes, where the main difference in expression between the two alleles was previously shown. Results: Nineteen and twenty-six TF genes were identified that responded to submergence in IR64 and IR64-Sub1, respectively. Only one gene was found to be submergence-responsive in both, suggesting different regulatory pathways under submergence in the two genotypes. These differentially expressed genes (DEGs) mainly included MYB, NAC, TIFY and Zn-finger TFs, and most genes were downregulated upon submergence. In IR64, but not in IR64-Sub1, SUB1B and SUB1C, which are also present in the Sub1 locus, were identified as submergence responsive. Four TFs were not submergence responsive but exhibited constitutive, genotype-specific differential expression. Most of the identified submergence responsive DEGs are associated with regulatory hormonal pathways, i.e. gibberellins (GA), abscisic acid (ABA), and jasmonic acid (JA), apart from ethylene. An in-silico promoter analysis of the two genotypes revealed the presence of allele-specific single nucleotide polymorphisms, giving rise to ABRE, DRE/CRT, CARE and Site II cis-elements, which can partly explain the observed differential TF gene expression. Conclusion: This study identified new gene targets with the potential to further enhance submergence tolerance in rice and provides insights into novel aspects of SUB1A-mediated tolerance. KW - Submergence tolerance KW - SUB1A KW - Rice KW - Transcription factors Y1 - 2018 U6 - https://doi.org/10.1186/s12284-017-0192-z SN - 1939-8425 SN - 1939-8433 VL - 11 IS - 2 PB - Springer Open CY - London ER -