COELHO, C. M.

GUIMARAES, P. E. O.

LOPES, M. A.

PAIVA, E.

VASCONCELOS, M. J. V.

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1364THE STRUCTURE ANO EXPRESSION OF ORCHIO EXTENSIN IN RESPONSETOWOUNDINGYen-Pin Lee and Saw-Hoon Lim_Schooi of Biological Sciences, National Universitv of Singapore, Singapore 1/9260Two cONAs coding for extensins have been isolated from Bromheadia finlavsoniana inorder 10 study lhe structure and expression of these proteins in orchids. The alignmem oftheir deduced amino acid sequences showed lhe eonsensus Ser-(Pro)4 rnotif thatchaructcriscs most cxtcnsins in higher plants. This rnotif was prescnt within tyrosine-richregions whieh may be involved in intramolecular and intermolecuíar cross-links 10 allow forlhe formation of a highly ordered irnpenetrable extensin barrier. A basallevel of extensintranscripts in lhe plant was observed. The effect of wounding on lhe expression of eXlensinswas then investigated and il was shown Ihal rhere was an accumulation of extensintranscriprs in lhe wounded leaves, h is also noteworthy that other mRNAs hybridize 10 thesecONAs and also accumulated in response to wounding. Such complexity is not unexpectedas some 01' lhe transcripts may represent othcr highly homologous extensin transcriptsprodueed from closely related members. This hypothcsis was substantiated as a Southernanalysis earried out dernonstrated that extensins belong to a multigene family in lhe B.finluvsoniana genome. ln addition to that, a sysrermc response 01'ao increase in cxtensintranscripts in young leaves was shown in this plant when one of its leavcs was wounded.Ovcrall, il is postulated that these proteins play nol only a siructural role in orehids bUI isalso involved in plant defense.1365GENETIC MANIPULATION OF PROTEIN QUALITY ANO QUANTITY IN MAIZEENOOSPERM.Mauricio A Lopes. Cíntia .M. Coelho. Paulo E. O. Guimarães. Edilson Paiva & Maria JoséV. Vasconcelos.National Mai:e and Sorghum Research Center (CNPMS) / Brazllian Agricultural ResearchCorporution (EMBRAPA). Rod.MG-424. km 65. c.r. /5/-Sete Lagoas. MG. CEP 3570/-970- Brazil.The maize kemel has low quantity and quality of proteins, Approximately 10% of themaize kemel's dry weight consists of di verse types of proteins. In addiuion, maize has lowcontem of lhe essential amino acids Iysine and tryptophan, whieh are nOI present in lhestorage protein fraction. zeins, accurnulated in lhe endosperm. Increasing lhe levei of theseamino acids has been a long-term goal of many breeding prograrns. Lysine contem in lheendosperm is primarily dependem on lhe amounl of non-zeins, which are proteins thatperform functions other than storage in lhe seed. We used lhe lIIinois High Protein (lHP)population and a high-quality protein population (CMS 52 QPM) 10 study the possibility 01'obtaining inbred lines with improved quality and higher protein arnounts. Many progenies(F2. F3 and BC) derived from crosses of llIinois High Protein x CMS-52 Quality ProteinMaize were Ihroughly evaluated at the biochemicallevel. Our results indicare greatvariability in protein panems among segregating materiais and lhe possibility of merging lhetraits high protein quality and high protein amount to develop materiais potentially useful inmaize breeding programs.Supported by: CNPq. F1NEPIPAOCT. and EMBRAPA.1366TISSUE CULTURE ANO TRANSFORMATION OF PEPEROMIA OBTUSIFOLlA.Haj-Sjm LQw1. Saw-Hoon Lim 2 and Sing-Kong Lee 3,l/nJtitute of Molecular Agrobiology. 59A The Fleming. / Science Park Drive, Singapore//8240 and 2Sehool of Biological Sciences. National University of Singapore. !I/ngapore119260 and 3School (lf Science, National Institute of Educatio •••Nanyang TechnologlcalUniversity, 469 Bukit Timan Road, Singapore 259756.Many speeies of Peperomia are used as indoor foliage plants. A tissue culture method forplant regeneration of Peperomia obtusifolia is described. Organogenesis was induced withleaf segments on Murashige and Skoog (MS) medium supplemented with 0.1 to 5.0 mgllindole acetic acid (lAA) and 0.1 to 5.0 mgll 6-benzyladenine (BA). Shoot multiplicationand root initiation occured within two months of culture under a 16h light and 8h dark cycleon high BA and IAA media respectively. Shoots were elongated by soaking in 5 mgllgibberellic acid (GA3) solution and readily formed roots on MS in the absence of growthregulators, forming full plantlets. Callus was produced on modified MS with a combinationof 2% glucose, 5 mglllhiamine. 0.1 mgll2.4-dichlorophenoxyacelic acid (2.4-0) and 0.2mgll kinetin, A protocol for Agrobacterium tumefaeiens-mediated transforrnation wasdeveloped for P.obtustfolia. Leaf segments were incubated on regeneration medium for 2days before co-culturing with A. tumefaciens LBA4404 carrying the binary veetor pBI 121.Transformants were selected on regeneration media supplemented with 30 mgll kanamycinand 200 mgll carbenicillin. A total of 8 lines obtained tested positive for both GUS stainingand Southern hybridization. Transient expression of GUS was also observed by particlebornbardrnent ofpBIl21 imo leafsegments.

Genetic manipulation of protein quality and quantity in maize endosperm.

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