PLANT PHYSIOLOGY: STUDY OF GROWTH AND PLANT ORGAN FUNCTION
CONTENTS HIGHER PLANT MITOCHONDRIA AS A SOURCE FOR NO NITRIC OXIDE A PRODUCT OF PLANT NITROGEN ASSIMILATION NO BASED SIGNALING IN PLANTS S NITROSYLATION IN PLANTS SPECTRUM AND SELECTIVITY ENZYMATIC SOURCES OF NITRIC OXIDE DURING SEED GERMINATION SEEKING THE ROLE OF NO IN BREAKING SEED DORMANCY NITRIC OXIDE FUNCTIONS AS INTERMEDIATE IN AUXIN ABSCISIC ACID AND LIPID SIGNALING PATHWAYS NITRIC OXIDE IN CYTOKININ AND POLYAMINE SIGNALING SIMILARITIES AND POTENTIAL CROSSTALK NITRIC OXIDE AND PLANT ION CHANNEL CONTROL NITRIC OXIDE IN NITROGEN FIXING SYMBIOSIS 1 15 35 53 73 91 112 130 152 172 NITROSATIVE STRESS IN PLANTS A NEW APPROACH TO UNDERSTAND THE ROLE OF NO IN ABIOTIC STRESS NITRIC OXIDE MEDIATED SIGNALING FUNCTIONS DURING THE PLANT HYPERSENSITIVE RESPONSE NITRIC OXIDE IN CELL TO CELL COMMUNICATION COORDINATING THE PLANT HYPERSENSITIVE RESPONSE MITOCHONDRIAL NITRIC OXIDE SYNTHESIS DURING PLANT PATHOGEN INTERACTIONS ROLE OF NITRATE REDUCTASE IN PROVIDING SUBSTRATES NITRIC OXIDE AS AN ALTERNATIVE ELECTRON CARRIER DURING OXYGEN DEPRIVATION FLUOROMETRIC DETECTION OF NITRIC OXIDE WITH DIAMINO UORESCEINS DAFS APPLICATIONS AND LIMITATIONS FOR PLANT NO RESEARCH 186 206 222 238 254 268 HIGHER PLANT MITOCHONDRIA AS A SOURCE FOR NO ABSTRACT HIGHER PLANT MITOCHONDRIA PRODUCE NITRIC OXIDE NO BY TWO SEPARATE SYS TEMS ONE IS A MITOCHONDRIAL NITRIC OXIDE SYNTHASE NOS WHICH CATALYZES THE SYNTHESIS OF NO AND L CITRULLINE FROM L ARGININE USING NAD P H THE OTHER ONE IS THE RESPI RATORY ELECTRON TRANSPORT CHAIN WITH THE TERMINAL OXIDASES CYTOX AND AOX WHICH BOTH REDUCE NITRITE TO NO WHILE OXYGEN IS OBLIGATORY FOR THE FORMER REACTION THE LAT TER ACTIVITY APPEARS VERY LOW IN AIR BUT HIGH UNDER OXYGEN DE CIENCY HOWEVER EVEN UNDER ANOXIA THE RATE OF NITRITE NO REDUCTION RARELY REACHES 1 OF RESPIRATORY ELECTRON TRANSPORT FOR AS YET UNKNOWN REASONS NITRITE NO REDUCTION APPEARS ABSENT IN MITO CHONDRIA FROM GREEN LEAVES THE CONTRIBUTION OF NOS AND OF NITRITE REDUCTION TO OVERALL NO PRODUCTION AND POSSIBLE FUNCTIONS OF NIRITE NO REDUCTION UNDER HYPOXIA ANOXIA ARE DISCUSSED 1 INTRODUCTION MITOCHONDRIA ARE KNOWN AS THE ORGANELLES HOUSING THE CITRIC ACID CYCLE AND MEMBRANE SYSTEMS FOR RESPIRATORY ELECTRON TRANSPORT AND OXIDATIVE PHOSPHO RYLATION THE BASIC STRUCTURAL SIMILARITY OF EUKARYOTIC MITOCHONDRIA RE ECTS AN OVERALL SIMILARITY IN THESE BASIC FUNCTIONS HOWEVER IN ADDITION MITO CHONDRIA SERVE MANY MORE IMPORTANT PURPOSES SUCH AS SYNTHESIS OF VITAMINS COFACTORS NUCLEOTIDES METABOLISM OF ORGANIC ACIDS AMINO ACIDS LIPIDS AND PARTIAL REACTIONS OF THE PHOTORESPIRATORY CYCLE REBEILLE ET AL 1997 BARTOLI ET AL 2000 GUEGUEN ET AL 2000 KOWALTKOWSKI 2000 FURTHER MITOCHONDRIA APPEAR TO PLAY AN IMPORTANT ROLE IN PROGRAMMED CELL DEATH BALK ET AL 1999 BALK AND LEAVER 2001 LAM ET AL 2001 ALSO COMPARE THE CONTRIBUTIONS IN THIS BOOK AND ARE A MAJOR SOURCE FOR REACTIVE OXYGEN SPECIES ROS FOR RE VIEW SEE M LLER 2001 THESE MULTIPLE FUNCTIONS ARE NOT EXPECTED TO OCCUR TO THE SAME EXTENT IN ALL PLANT ORGANS BUT ARE MORE OR LESS EXPRESSED IN SPECI C ORGANS CELL TYPES AND DEVELOPMENTAL STAGES RECENTLY EVIDENCE HAS BEEN ACCUMULATING THAT MITOCHONDRIA ARE ALSO INVOLVED IN TWO APPARENTLY OP POSED PROCESSES NAMELY THE PRODUCTION BUT ALSO THE CONSUMPTION OF NITRIC OXIDE NO AS NO HAS GAINED INCREASING ATTENTION IN PLANTS AS A SIGNALING COMPOUND AS WELL AS A HIGHLY REACTIVE MODIFYING AGENT FOR BIOMOLECULES INCLUDING PROTEINS THIS NEW MITOCHONDRIAL FUNCTION APPEARS POTENTIALLY IM 1 PORTANT THUS WE WILL BRIE Y SUMMARIZE PRESENT KNOWLEDGE ON NO IN CONTEXT WITH MITOCHONDRIA 2 NO PRODUCTION PLANTS APPEAR TO PRODUCE NO BY TWO BASICALLY DIFFERENT PATHWAYS ALSO COM PARE FIG 1 1 THE L ARGININE DEPENDENT PATHWAY USES NAD P H AND O2 AS COSUBSTRATES AND IS CATALYZED BY NITRIC OXIDE SYNTHASE NOS ACCORDING TO REACTION 1 L ARG NAD P H H O2 L CITR NAD P NO 1 2 THE NITRITE DEPENDENT PATHWAY USES NADH OR ELECTRONS AS REDUCTANDS AND IS CATALYZED BY A NUMBER OF DIFFERENT ENZYMES ACCORDING TO REAC TION 2 NO2 E 2H 2NO H2O 2 IN PLANTS REDUCTION OF NITRITE TO NO WAS ORIGINALLY THOUGHT TO BE ONLY CAT ALYZED BY NITRATE REDUCTASES NR XANTHINE OXIDASE DEHYDROGENASE XDH FIG 1 REACTIONS PRODUCING NO IN PLANT MITOCHONDRIA NITRIC OXIDE SYNTHASE NOS HAS BEEN SHOWN IN ARABIDOPSIS TO PRODUCE NO FROM L ARGININE IMPORTED FROM THE CYTOSOL NOS ATNOS1 IS PROBABLY INTEGRATED INTO THE INNER MEMBRANE NO CAN BE ALSO PRODUCED BY MITOCHONDRIAL ELECTRON TRANSPORT REDUCING NITRITE TO NO THE FORMATION OF NO FROM NO2 DOES NOT REQUIRE OXYGEN AND IS REPRESENTED BY A DOTTED ARROW THE REACTION IS HARDLY DETECTABLE IN AIR ONE POSSIBLE EXPLANATION IS COMPETITION WITH OXYGEN FOR FURTHER DETAILS SEE TEXT CYT OX CYTOCHROME OXIDASE AOX ALTERNATIVE OXIDASE 2 HAS ALSO BEEN OCCASIONALLY SUGGESTED AS A SOURCE FOR NO USING NITRITE AND XAN THINE AS A SUBSTRATE MILLAR ET AL 1998 GODBER ET AL 2000 HOWEVER OUR OWN EXPERIMENTS USING RECOMBINANT XDH GAVE NO EVIDENCE FOR NO PRODUCTION BY THE ENZYME ITSELF MENDEL AND KAISER UNPUBLISHED NON ENZYMATIC NO PRODUCTION FROM NITROUS ACID ACCORDING TO EQ 3 SHOULD OCCUR AT SIGNI CANT RATES ONLY AT PH VALUES BELOW PH 5 PKA 3 2 OF NITROUS ACID 2HNO2 NO NO2 H2O 2NO 1 2O2 H2O 3 CONDITIONS FAVORING NON ENZYMATIC NO FORMATION ARE PROBABLY RARE BUT OC CASIONALLY THEY MAY BE MET IN THE APOPLAST OF PLANT CELLS BETHKE ET AL 2004 AND PERHAPS ALSO IN THE VACUOLES OVERALL THE CONTRIBUTION OF XDH AND OF NON ENZYMATIC NO FORMATION TO OVERALL PLANT NO PRODUCTION SEEMS NEGLIGIBLE COMPARED TO THE CONTRIBUTION OF NR HOWEVER ACCORDING TO MORE RECENT RESEARCH MITOCHONDRIA ARE AN OTHER IMPORTANT SOURCE FOR NO IN PLANTS AND INDEED BOTH REACTIONS 1 AND 2 APPEAR TO OCCUR INSIDE PLANT MITOCHONDRIA AS WILL BE SHOWN 2 1 NITRIC OXIDE SYNTHASE IS LOCATED IN THE MITOCHONDRIA THE ABOVE MENTIONED NITRIC OXIDE SYNTHASE NOS REACTION WAS SUGGESTED AS A SOURCE FOR NO IN PLANTS MAINLY BASED ON PHARMACOLOGICAL EVIDENCE INHI BITION OF NO FORMATION OR OF NO DEPENDENT REACTIONS BY CHEMICAL ANALOGS OF L ARGININE IS USUALLY TAKEN AS AN INDICATION THAT THE REACTION WAS TRIGGERED BY NOS DERIVED NO IMMUNOLOGICAL EVIDENCE FOR NOS IN PLANTS WAS OBTAINED WITH ANTIBODIES AGAINST ANIMAL NOS KUO ET AL 1995 SEN AND CHEMA 1995 BARROSO ET AL 1999 RIBIERO ET AL 1999 BUT THOSE ANTIBODIES PROVED TO BE RATHER UNSPECI C LO ET AL 2000 BUTT ET AL 2003 AS NO ARABIDOPSIS GENE OR PROTEIN HOMOLOG TO THE LARGE AND COMPLEX ANIMAL PROTEIN HAS YET BEEN FOUND THE EXISTENCE OF NOS IN PLANTS IS STILL AN ENIGMA MORE RECENTLY A BREAKTHROUGH IN NO RESEARCH WAS ACHIEVED BY THE ND ING OF THE CRAWFORD GROUP GUO ET AL 2003 CRAWFORD AND GUO 2005 THAT ARABIDOPSIS CONTAINS A GENE WITH SEQUENCE SIMILARITY TO A GENE FROM HELIX POMATIA THAT IS IMPLICATED IN NO SYNTHESIS THE GENE ENCODES A 60 KDA PRO TEIN WHICH WHEN EXPRESSED IN E COLI INCREASED NO SYNTHESIS IN CELL EXTRACTS WHEN THE CORRESPONDING GENE ATNOS1 WAS KNOCKED OUT IN ARABIDOPSIS THE RESULTING MUTANT HAD REDUCED NO PRODUCTION IN ROOTS MEASURED WITH DAF 2DA CONTRARY TO ANIMAL NOS ABOUT 140 KDA THE MUCH SMALLER ATNOS1 REQUIRES NO AVIN OR TETRAHYDROBIOPTERIN BUT ONLY CA2 CAM AND NADPH ATNOS1 SEEMS CONSTITUTIVELY EXPRESSED IT HAS BEEN SUGGESTED TO BE PART OF THE SIGNALING PATHWAY INVOLVED IN ABA INDUCED STOMATAL CLOSURE GERMINA TION ROOT AND SHOOT GROWTH SEED FERTILITY FOR REVIEW CRAWFORD AND GUO 2005 CONTROL OF OWER TIMING HE ET AL 2004 SENESCENCE AND PROTECTION AGAINST OXIDATIVE DAMAGE GUO AND CRAWFORD 2005 AND SEEMS ALSO INVOLVED 3