03883naa a2200253 a 450000100080000000500110000800800410001910000200006024502020008026000090028252030210029165300130331265300200332565300090334565300120335470000190336670000230338570000210340870000150342970000190344470000190346370000170348277301300349911248562016-02-18       2015    bl uuuu     u00u1 u    #d1 aLAVINSKI, A. O.  aSILICON ENHANCES ROOT DIAMETER AND AERENCHYMA FORMATION AND INDUCES CHANGES IN METABOLISM AND FERMENTATIVE PATHWAY IN WATERLOGGED RICE PLANTS VIA ETHYLENE-SIGNALING PATHWAYS.h[electronic resource]  c2015  aIn stagnant culture solutions, we have previously identified altered morphology of roots (i.e.,  thicker  and  shorter  roots)  of  rice  (Oryza  sativa  L.)  plants  when  supplemented  with  silicon  (Si).  Here,  we  hypothesized  that  Si  may  exert  its  effects  on  root  morpho-anatomical  traits  through a ethylene signaling pathways. To clarify the relationship between Si and root traits  we  first  conducted  a  root  structural/anatomical  characterization  of  rice  plants  supplemented  with Si and then the underlying mechanisms were investigated  by combining hormonal and  metabolite profiles with expression of a range of genes presumably affected by ethylene. Si  addition did not alter root biomass, but led to decreases in root length together with increased  root  diameter.  In  +Si  plants,  there  was  a  geater  suberization  of  schlerenchyma  and  lignification of the endodermis and exodermis, whereas in  ?Si plants differential lignification  was only observed in the exodermis. Si was also associated with remarkable increases in the  cross-sectional  areas  of  vasculature  (93%),  xylem  vessels  (50%),  cortex  (92%)  and  particularly  aerenchyma  (448%).  Relative  to  ?Si  plants,  their  +  Si  counterparts  displayed  lower  (80%)  concentration  of  ACC  (the  immediate  ethylene  precursor)  in  parallel  to  remarkable  higher  concentrations  of  ethylene  (600%),  salicylic  acid  (300%)  and  jasmonic  acid  (2500%),  whereas  the  pools  of  indol-3-acetic  acid  (auxin)  and  abscisic  acid  were  unresponsive to Si. In the +Si plants, we observed a global up-regulation of transcripts from  genes associated with ethylene biosynthesis (in some cases exceeding 200 times, e.g., ACC  oxidase and the homologue for ACC synthase). Overall, Si nutrition caused an up-regulation  of a range of genes associated with synthesis of lignin and suberin and genes associated  with  acclimation  responses  of  rice  to  submergence  whose  expressions  are  triggered  by  ethylene,  with significantly higher abundance for  Sub1B  (10 fold) and  SK1  (100 fold). Overall, Si did  not affect the root levels of sugars, but it reduced the levels of organic acids associated with  the  tricarboxylic  acid  cycle  and  increased  a  range  of  amino  acids.  Our  data  suggest  an  upregulation  of  fermentative  pathway,  in  line  with  an  up-regulation  of  genes  encoding  for  enzymes related to the anaerobic pathway. However,  increases in fermentative pathway seem  not to be associated with hypoxic conditions but they could simply be an additional route to supply  energy  that  is  required  for  several  energy-consuming  processes  that  seem  strongly  upregulated in the +Si plants such  as biosynthesis of cell wall components. In summary, Si  apparently triggers ethylene production which in turn seems to induce a range of molecular  and metabolic alterations that culminate with the observed changes in root anatomy upon Si  supplementation.  aFlooding  aGene expression  aRice  aSilicon1 aDETMANN, K. C.1 aSANGLARD, L. M. V.1 aRODRIGUES, F. A.1 aARAUJO, L.1 aRIBEIRO, D. M.1 aARA??JO, W. L.1 aMATTA, F. M.  tIn: BRAZILIAN CONGRESS OF PLANT PHYSIOLOGY, 15., 2015, Foz do Igua??u, Paran??, Brazil . Annals... Rio Claro, SP: SBFV, 2015.