Traditionally, calmodulin (CaM) was thought to be a multi-functional receptor for intracellular Ca2+ signals. But in the last ten years, it was found that CaM also exists and acts extracellularly in animal and plant c...Traditionally, calmodulin (CaM) was thought to be a multi-functional receptor for intracellular Ca2+ signals. But in the last ten years, it was found that CaM also exists and acts extracellularly in animal and plant cells to regulate many important physiological functions. Laboratory studies by the authors showed that extracellular CaM in plant cells can stimulate the proliferation of suspension cultured cell and protoplast; regulate pollen germination and pollen tube elongation,and stimulate the light-independent gene expression of Rubisco small subunit (rbcS). Furthermore,we defined the trans-membrane and intracellular signal transduction pathways for extracellular CaM by using a pollen system. The components in this pathway include heterotrimeric G-protein,phospholipase C, IP3, calcium signal and protein phosphorylation etc. Based on our findings, we suggest that extracellular CaM is a polypeptide signal in plants. This idea strongly argues against the traditional concept that there is no intercellular polypeptide signal in plants.展开更多
IN recent years, calmodulin （CaM）, an important Ca<sup>2+</sup> receptor and constituent of cellular signal transduction systems, has been found extracellularly. We have verified that CaM is presented ex...IN recent years, calmodulin （CaM）, an important Ca<sup>2+</sup> receptor and constituent of cellular signal transduction systems, has been found extracellularly. We have verified that CaM is presented extracellularly in all of plant species we have examined. In addition, we have reported that extracellular CaM has some biological significance, such as stimulation of cell proliferation, cell wall regeneration, initiation of pollen germination and tube growth and inducement of rbcS gene expression. The role of heterotrimeric G proteins in pollen germination, tube growth and signal transduction of extracellular CaM has been examined in Lily pollen, and two kinds of antibodies against animal Gzα internal sequence and N-terminal展开更多
Extracellular calmodulin (CaM) plays significant roles in many physiological proc-esses,but little is known about its mechanism of regulating stomatal movements. In this paper, whether CaM exists in the guard cell wal...Extracellular calmodulin (CaM) plays significant roles in many physiological proc-esses,but little is known about its mechanism of regulating stomatal movements. In this paper, whether CaM exists in the guard cell walls of Arabidopsis and whether depolymerization of actin cytoskeleton is involved in extracellular CaM-induced stomatal closing are investigated. It is found that CaM exists in guard cell walls of Arabidopsis, and its molecular weight is about 17 kD. Bioassay using CaM antagonists W7-agarose and anti-CaM serum shows that the endogenous extracellular CaM promotes stomatal closure and delays stomatal opening. The long radial actin filaments in guard cells undergo disruption in a time-dependent manner during exogenous CaM-induced stomatal closing. Pharmacological experiments show that depolymerization of ac-tin cytoskeleton enhances the effect of exogenous CaMinduced stomatal closing and polym-erization reduces the effect. We also find that exogenous CaM triggers an increase in [Ca2+]cyt of guard cells. If [Ca2+]cyt increase is blocked with EGTA, exogenous CaM-induced stomatal closure is inhibited. These results indicate that extracellular CaM causes elevation of [Ca2+]cyt in guard cells, subsequently resulting in disruption of actin filaments and finally leading to guard cells closure.展开更多
The role of extracellular calmodulin in regulating expression of rbcS in darkness was examined. A suspension-cultured cell line was generated from the transgenic rbcS-GUS tobacco. It was demonstrated that purified cal...The role of extracellular calmodulin in regulating expression of rbcS in darkness was examined. A suspension-cultured cell line was generated from the transgenic rbcS-GUS tobacco. It was demonstrated that purified calmodulin added to the media enhanced rbcS-GUS expression. The time course of expression of rbcS-GUS and that of the secretion of calmodulin in the suspended transgenic tobacco cells in darkness were very similar. Both showed initial increase followed by decline with maximum calmodulin secretion preceding maximum GUS expression. The addition of membrane-impermeable calmodulin antagonist W7-agarose inhibited the expression of rbcS-GUS in darkness, but this inhibitory effect was completely reversed by adding exogenous purified calmodulin. These results provide the first evidence that extracellular calmodulin accelerates rbcS gene expression.展开更多
The effects of calmodulin (CaM) antagonist W7_agarose, anti_CaM serum and exogenous purified CaM on pollen germination and tube growth of Forsythia suspensa were studied. The pollen germination and tube growth were in...The effects of calmodulin (CaM) antagonist W7_agarose, anti_CaM serum and exogenous purified CaM on pollen germination and tube growth of Forsythia suspensa were studied. The pollen germination and tube growth were inhibited or completely stopped by CaM antagonist W7_agarose. The addition of exogenous purified CaM stimulated pollen germination and tube growth, whereas the same amount of bovine serum albumin (BSA) had no effect. The inhibitory effects caused by W7_agarose and anti_CaM serum could be reversed completely by the addition of exogenous purified CaM. The tube growth of germinated pollen was also inhibited or completely stopped by W7_agarose. The results suggest that endogenous extracellular CaM initiates pollen germination and tube growth, whereas exogenous CaM enhances the above processes.展开更多
In our previous reports, wehave verified the involvement of G protein, Ca2+ channel in plasma memband CDPK in extracellular calmodulin(CaM) signal transduction chain for theinitiatory effects of extracellular CaM onpo...In our previous reports, wehave verified the involvement of G protein, Ca2+ channel in plasma memband CDPK in extracellular calmodulin(CaM) signal transduction chain for theinitiatory effects of extracellular CaM onpollen germination and pollen tubegrowth . In this paper, both normal andexogenous CaM-enhanced pollen germination and tube growth were completelyinhibited by the phospholipase C inhibitor U-73122 (Fig. 1 ). The enhancement of pollen germination and tubegrowth by the G protein agonist choleratoxin were also completely inhibited byU-73122 (Fig. 2), whereas the inhibition of pollen germination and tubegrowth by the G protein antagonist pertussis toxin was reversed by IP3 (Fig. 2).Heparin, an antagonist Of IP3 receptor,inhibited pollen germination and tubegrowth (Fig. 3 ), while thapsigargin increased cytosolic Ca2+ by inhibiting theIP3-specific Ca2+ pump in endoplasmicreticulum, and thereby increased pollengermination and tube growth (Fig. 4).The above results suggest that phosphoinositide signaling pathway might be involved in the extracellular CaM signaltransduction chain in the initiatory effectsof extracellular CaM on pollen germination and tube growth.展开更多
The molecular weight of bovine brain CaM, intracellular CaM and extracellularCaM of cauliflower have been determined for the first time by Matrix-Assisted Larer Desorp tion Ionization Time of Flight Mass Spectrometry(...The molecular weight of bovine brain CaM, intracellular CaM and extracellularCaM of cauliflower have been determined for the first time by Matrix-Assisted Larer Desorp tion Ionization Time of Flight Mass Spectrometry(MALDI-TOF-MS). The molecular weightof bovine brain CaM, 16 699. 9 Da determined by MALDI-TOF-MS, is closely ideatical with16 700 Da, calculated from its primary sequence, showing the high accuracy of MALDITOF-MS and the conf1rmation of previously determined sequence. Furthermore, the molecular weight of intracellular CaM and extracellular CaM determined by MAlDI-TOF-MS, 17025 Da and 15 582 Da, are in agreement with 17 500 Da and 15 000 Da determined by SDSPAGE-This agreement shows the high accuracy of MALDI-TOF-MS. In addition, themolecular weight of CaMs with this technique can be determined rapidly(less than 10 min)and sensitively.展开更多
基金the National NaturalScience Foundation of China (Grant Nos. 39730230, 39870365), the National Key Basic Research Special Funds of China (Grant No. G19990117) and the National Outstanding Young Scientist Fellowship of China (Grant No. 30025024).
文摘Traditionally, calmodulin (CaM) was thought to be a multi-functional receptor for intracellular Ca2+ signals. But in the last ten years, it was found that CaM also exists and acts extracellularly in animal and plant cells to regulate many important physiological functions. Laboratory studies by the authors showed that extracellular CaM in plant cells can stimulate the proliferation of suspension cultured cell and protoplast; regulate pollen germination and pollen tube elongation,and stimulate the light-independent gene expression of Rubisco small subunit (rbcS). Furthermore,we defined the trans-membrane and intracellular signal transduction pathways for extracellular CaM by using a pollen system. The components in this pathway include heterotrimeric G-protein,phospholipase C, IP3, calcium signal and protein phosphorylation etc. Based on our findings, we suggest that extracellular CaM is a polypeptide signal in plants. This idea strongly argues against the traditional concept that there is no intercellular polypeptide signal in plants.
文摘IN recent years, calmodulin （CaM）, an important Ca<sup>2+</sup> receptor and constituent of cellular signal transduction systems, has been found extracellularly. We have verified that CaM is presented extracellularly in all of plant species we have examined. In addition, we have reported that extracellular CaM has some biological significance, such as stimulation of cell proliferation, cell wall regeneration, initiation of pollen germination and tube growth and inducement of rbcS gene expression. The role of heterotrimeric G proteins in pollen germination, tube growth and signal transduction of extracellular CaM has been examined in Lily pollen, and two kinds of antibodies against animal Gzα internal sequence and N-terminal
文摘Extracellular calmodulin (CaM) plays significant roles in many physiological proc-esses,but little is known about its mechanism of regulating stomatal movements. In this paper, whether CaM exists in the guard cell walls of Arabidopsis and whether depolymerization of actin cytoskeleton is involved in extracellular CaM-induced stomatal closing are investigated. It is found that CaM exists in guard cell walls of Arabidopsis, and its molecular weight is about 17 kD. Bioassay using CaM antagonists W7-agarose and anti-CaM serum shows that the endogenous extracellular CaM promotes stomatal closure and delays stomatal opening. The long radial actin filaments in guard cells undergo disruption in a time-dependent manner during exogenous CaM-induced stomatal closing. Pharmacological experiments show that depolymerization of ac-tin cytoskeleton enhances the effect of exogenous CaMinduced stomatal closing and polym-erization reduces the effect. We also find that exogenous CaM triggers an increase in [Ca2+]cyt of guard cells. If [Ca2+]cyt increase is blocked with EGTA, exogenous CaM-induced stomatal closure is inhibited. These results indicate that extracellular CaM causes elevation of [Ca2+]cyt in guard cells, subsequently resulting in disruption of actin filaments and finally leading to guard cells closure.
文摘The role of extracellular calmodulin in regulating expression of rbcS in darkness was examined. A suspension-cultured cell line was generated from the transgenic rbcS-GUS tobacco. It was demonstrated that purified calmodulin added to the media enhanced rbcS-GUS expression. The time course of expression of rbcS-GUS and that of the secretion of calmodulin in the suspended transgenic tobacco cells in darkness were very similar. Both showed initial increase followed by decline with maximum calmodulin secretion preceding maximum GUS expression. The addition of membrane-impermeable calmodulin antagonist W7-agarose inhibited the expression of rbcS-GUS in darkness, but this inhibitory effect was completely reversed by adding exogenous purified calmodulin. These results provide the first evidence that extracellular calmodulin accelerates rbcS gene expression.
文摘The effects of calmodulin (CaM) antagonist W7_agarose, anti_CaM serum and exogenous purified CaM on pollen germination and tube growth of Forsythia suspensa were studied. The pollen germination and tube growth were inhibited or completely stopped by CaM antagonist W7_agarose. The addition of exogenous purified CaM stimulated pollen germination and tube growth, whereas the same amount of bovine serum albumin (BSA) had no effect. The inhibitory effects caused by W7_agarose and anti_CaM serum could be reversed completely by the addition of exogenous purified CaM. The tube growth of germinated pollen was also inhibited or completely stopped by W7_agarose. The results suggest that endogenous extracellular CaM initiates pollen germination and tube growth, whereas exogenous CaM enhances the above processes.
文摘In our previous reports, wehave verified the involvement of G protein, Ca2+ channel in plasma memband CDPK in extracellular calmodulin(CaM) signal transduction chain for theinitiatory effects of extracellular CaM onpollen germination and pollen tubegrowth . In this paper, both normal andexogenous CaM-enhanced pollen germination and tube growth were completelyinhibited by the phospholipase C inhibitor U-73122 (Fig. 1 ). The enhancement of pollen germination and tubegrowth by the G protein agonist choleratoxin were also completely inhibited byU-73122 (Fig. 2), whereas the inhibition of pollen germination and tubegrowth by the G protein antagonist pertussis toxin was reversed by IP3 (Fig. 2).Heparin, an antagonist Of IP3 receptor,inhibited pollen germination and tubegrowth (Fig. 3 ), while thapsigargin increased cytosolic Ca2+ by inhibiting theIP3-specific Ca2+ pump in endoplasmicreticulum, and thereby increased pollengermination and tube growth (Fig. 4).The above results suggest that phosphoinositide signaling pathway might be involved in the extracellular CaM signaltransduction chain in the initiatory effectsof extracellular CaM on pollen germination and tube growth.
文摘The molecular weight of bovine brain CaM, intracellular CaM and extracellularCaM of cauliflower have been determined for the first time by Matrix-Assisted Larer Desorp tion Ionization Time of Flight Mass Spectrometry(MALDI-TOF-MS). The molecular weightof bovine brain CaM, 16 699. 9 Da determined by MALDI-TOF-MS, is closely ideatical with16 700 Da, calculated from its primary sequence, showing the high accuracy of MALDITOF-MS and the conf1rmation of previously determined sequence. Furthermore, the molecular weight of intracellular CaM and extracellular CaM determined by MAlDI-TOF-MS, 17025 Da and 15 582 Da, are in agreement with 17 500 Da and 15 000 Da determined by SDSPAGE-This agreement shows the high accuracy of MALDI-TOF-MS. In addition, themolecular weight of CaMs with this technique can be determined rapidly(less than 10 min)and sensitively.
