Document:

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                                                                  EXHIBIT 10.5.2

                             ADDENDUM ("ADDENDUM")
                          TO THAT REAL PROPERTY LEASE
                            DATED JANUARY 25, 1997,
                 BY AND BETWEEN MARTIN P. HULL, MIEKE DANKERS,
               DENNIS W. ROYER, AND CHRISTINE J. ROYER ("LESSOR")
                                      AND
                  DELTAGEN, A DELAWARE CORPORATION ("LESSEE")

PARAGRAPH 1.2 CONTINUED:

         The  Premises are more fully  described  by way of a legal
description contained in Exhibit A, attached hereto.

PARAGRAPH 1.4 CONTINUED.  EARLY POSSESSION.

         Upon execution of this Lease, Lessee shall have the right to occupy
the Premises for the purpose of constructing its improvements therein. Lessee
agrees not to interfere with the work of Lessor.  In the event Lessee's work
interferes with  Lessor's  ability to complete  its work and to  commence
the term of this Lease,  then the Lease term shall commence on the date
Lessor would have had the Premises available for occupancy but for the delay
caused by Lessee.

PARAGRAPH 1.5 CONTINUED:

         Rent is payable on the first day of each month,  commencing on March
1, 1997.  However,  should  Lessor  complete  those items it has agreed to do
under Paragraph 50 of the Addendum prior to March 1, 1997, then the Lease
Commencement Date shall be the date that Lessor  completed  its work,  and
Lessee shall pay a pro rated Base Rent for the partial month. In the event
Lessor fails to complete its work, under the terms of the Lease, and the work
is completed after March 1, 1997,  then the Lease  Commencement  Date shall
be the latter  date and the Base Rent shall be pro rated.

PARAGRAPH 2.2. CONTINUED:

         Lessor agrees to transfer to Lessee, as of the Lease Commencement
Date, any  warranties  Lessor has for work  performed by Lessor or its
contractors or agents within the Premises.

PARAGRAPH 6.2(a). CONTINUED:

         Lessor  acknowledges  and  consents to Lessee's  use of the
"Hazardous Substances"  disclosed  in  Lessee's  Application  for
Conditional  use  Permit submitted to and approved by the City of San Carlos.

PARAGRAPH 6.2(d). CONTINUED:

         A new Paragraph, 6.2(d) is included in the Lease as follows:

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         Lessor  shall  indemnify,   protect,   defend  and  hold  Lessee,
its shareholders,  officers,  directors,  employees  and  agents  harmless
from and against  any and all losses  and/or  damages,  liabilities,
judgements,  costs, claims, liens, expenses,  penalties,  permits and
attorney's fees and consulting fees  arising  out of or  involving  any
Hazardous  Substance  in or below  the Premises which existed prior to the
commencement  date of this Lease,  or which entered upon or under the
Premises, after the Lease Commencement Date, resulting from the actions of
others than Lessee,  its employees,  contractors,  invitees, agents or others
within the control of Lessee.  Lessor's  obligations under this Paragraph  6
shall  include,   but  not  be  limited  to  the  effects  of  any
contamination  or injury to  person,  property,  or the  environment  created
or suffered  by  Lessee or  others,  and the cost of the  investigation
(including consultants and attorneys' fees and testing, removal,
remediation,  restoration and/or  abatement  thereof) or any  contamination
therein  involved,  and shall survive the  expiration  or early  termination
of this Lease.  No  termination, cancellation  or release  agreement  entered
into by Lessee shall release Lessor from its  obligations  under this Lease
with respect to Hazardous  Substances or storage tanks, unless specifically
agreed to by Lessee in writing at the time of such agreement.

         Lessee shall notify Lessor in writing immediately upon discovery of
any facts on which Lessee may base a claim for indemnification under this
Paragraph.

PARAGRAPH 6.3 CONTINUED:

         Lessee shall, at Lessee's sole cost and expense, fully, diligently,
and in a timely  manner,  comply  with all  "Applicable  Law"  relating  to
Lessee's specific occupancy of the Premises. Lessee shall, within five days
after receipt of Lessor's  written  request,  provide  Lessor with copies of
all documents and information,  including, but not limited to, permits,
registrations,  manifests, applications, reports and certificates,
evidencing Lessor's compliance with any Applicable Law, and shall
immediately,  upon receipt, notify Lessor, in writing, of any  threatened  or
actual claim,  notice,  citation,  warning,  complaint or report  pertaining
to or  involving  failure  by  Lessee  to  comply  with  any Applicable Law.
"Applicable Law" for purposes of this Agreement,  shall mean all federal,
state and local law, ordinances, regulations and permits required.

PARAGRAPH 7.1 CONTINUED:

         Notwithstanding  anything else  contained in the Lease to the
contrary, Landlord  shall be responsible  for all structural  repairs and
Paragraph 7.1 is subject to the terms and conditions contained in Paragraph
50 of the Addendum.

PARAGRAPH 7.4. CONTINUED:

         Notwithstanding  anything else in the Lease to the  contrary,
Lessee's "trade  fixtures" will remain the property of Lessee,  and Lessee
shall have the right to remove all of its trade fixtures at the termination
of this Lease.

PARAGRAPH 8.7 CONTINUED:

         Except for Lessee's  negligence  and/or  breach of express
warranties, Lessor shall indemnify,  protect, defend and hold harmless the
Premises,  Lessee and its agents,  shareholders and lenders from and against
any and all claims, loss of rents and/or damages, costs, liens,

                                      -2-
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judgements, penalties, permits, attorney's and consultant's fees, expenses
and/or liabilities arising out of, involving or in dealing with Lessor's
ownership of the Premises, any act, omission or neglect of Lessor, its
agents, contractors, employees or invitees, and out of any default or breach
by Lessor in the performance in a timely manner of any obligation of Lessor's
part to be performed under this Lease. The foregoing shall include, but not
be limited to, the defense or pursuit of any claim or any action or
proceeding involved therein, and whether or not (in the case of claims made
against Lessee) litigated and/or reduced to judgment, and whether well
founded or not. In case any action or proceeding by brought against Lessee by
reason of any of the foregoing matters, Lessor, upon notice from Lessee,
shall defend the same at Lessor's expense by counsel reasonably satisfactory
to Lessee and Lessee shall cooperate with Lessor in such defense. Lessee need
not have first paid any such claim in order to be so indemnified.

         Lessor shall notify Lessor in writing  immediately upon discovering
any facts  upon  which  Lessee  may  base a claim  for  indemnification
under  this Paragraph.

PARAGRAPH 16.2 CONTINUED:

         Notwithstanding  anything else contained to the contrary in this
Lease, Lessee's  obligation  to  provide  financial  statements  shall be
specifically limited to the prior year's financial  statements and its most
current financial statement.  Lessee shall not be required to provide this
financial  information more than twice during the term of the Lease.

PARAGRAPH 39.2 CONTINUED:

         Notwithstanding  anything else to the contrary contained herein,
Lessee shall have the right to assign this Lease to any affiliated company or
successor entity,  and said affiliated company or successor entity shall have
the right to exercise any options granted under the terms of this Lease.

PARAGRAPH 49.

         Lessor estimates that Lessee's  expenses,  reimbursable to Lessor,
are approximately $2,000.00 per month.

PARAGRAPH 50.

         Lessor  agrees to pay for,  construct,  install,  repair or perform
the following, prior to the Lease Commencement Date:

         a.       All general building systems, such as the heating,
                  ventilating and air conditioning (HVAC),
                  electrical-systems, plumbing systems, hardware, locking
                  mechanisms, roll up doors, light bulbs, tubes and  ballasts
                  and the like shall be repaired and in good working order
                  and capable of functioning in the manner for which they
                  were intended.  Lessor shall not be responsible for
                  repairing any specialty equipment installed by Lessee.
                  Lessor, at Lessor's sole cost and expense, shall install a
                  standard phone line to the building.

                                      -3-
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         b.       The  building  shall be repaired and restored in a matter
                  that will enable it to be free from water  intrusion  from
                  leaks in the walls,  roof,  windows,  floors and doors.
                  Existing water damage shall be repaired  and  replaced by
                  the Lessor.  Lessee shall  have no  liability  for  repair
                  or  replacement  of any flooring within the Premises, which
                  flooring is damaged due to water intrusion into the
                  Premises,  the cause of which was not Lessee's.

         c        With regard to the presence of Hazardous Substances or the
                  presence of toxics within the Building, Lessor agrees to:

                  (1)      Remove all existing Hazardous Substances and toxics.

                  (2)      All of the hoods, vents, ducting and piping
                           associated with the lab areas shall be removed,
                           with all penetrations properly repaired and patched.

                  (3)      With regard to the "sump room" Lessor shall obtain a
                           closure report for that room. All equipment, drains,
                           and the like shall be removed and concrete shall be
                           poured over the opening in the floor so that the
                           floor is made level with the adjoining rooms. The
                           discharge drainage line in this room shall be
                           pressure tested to ensure that it did not leak.
                           Lessee shall have the right, at Lessee's cost, to
                           take core samples of the soil underneath this room
                           and have those soil samples tested to ensure that no
                           Hazardous Materials or toxic waste is found therein.
                           Lessor shall comply with all other requirements of
                           the County of San Mateo to obtain an appropriate
                           closure report.

                  (4)      Lessor shall have obtained a final closure report
                           from the County of San Mateo, for the Premises.

         d.       Lessor and Lessee agree that Lessee's maintenance
                  obligations with  regard  to  the  HVAC  units,  shall  be
                  restricted  to $4,800.00 per year.  The cost of
                  maintaining or operating the HVAC  units over and above
                  this  amount  shall be paid for by Lessor.

         e.       At the rear of the building there is a "chiller". The
                  chiller, all piping and equipment  associated with it,
                  shall be removed and all holes patched and repaired by
                  Lessor.

         f.       Lessor  agrees to patch and repair all roof leaks prior to
                  the Lease  Commencement  Date, and to guarantee to repair
                  any roof leaks which manifests  themselves  during the
                  first six months of the Lease term.

         g.       Lessor  agrees to employ a  structural  engineer to review
                  the structural  integrity of the roof system.  The engineer
                  shall specifically investigate the condition of the hangars
                  used to support the roof framing  members, many of which
                  are corroded and rusted.  The integrity of the roof shall
                  be  investigated, and repaired at the cost of Lessor.  At
                  the time of this repair, the foil paper installed in the
                  ceiling shall be removed. Lessor agrees to install
                  insulation above the drop ceiling throughout the

                                      -4-
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                  Premises. Lessee shall have no liability for the repair or
                  replacement of any portion of the Premises as a result of
                  condensation damage to the building.

         h.       The soffit at the front of the building is not secure.
                  Lessor agrees to,  secure the wooden  members so that they
                  may not be removed to allow entry into the Premises.

         i.       At the back of the building, above the roll up door, is a fan.
                  Lessor shall remove the fan and patch and repair the hole.

         j.       Lessor shall repair the exposed electrical wire to the
                  landscaping timer.

         k.       The fire sprinkler riser, at the front of the Building, is
                  set on an angle.  Lessee  shall have no liability
                  whatsoever  for correcting  this  deficiency  or for any
                  damage  caused by its current condition.

         l.       Lessor and Lessee  acknowledge  that the back  parking  lot
                  is prone to flooding.  Currently,  the parking lot is not
                  in good physical  condition,  due to recent  and past
                  floods.  Lessor agrees to repair  this  parking  lot and
                  Lessee  shall have no liability  for its  maintenance
                  throughout  the  term of this Lease except as to damage
                  specifically caused by Lessees.

         m.       At the front left corner of the building, there is a
                  downspout located near the  electrical  box for the
                  adjoining  building. Lessee shall have no liability to
                  Lessor or to any other third parties as a result of this
                  configuration.

         n.       All  cracks in the  cinder  block  building  material  for
                  the exterior of the  building,  shall be repaired so that
                  they are water tight.

         o.       Currently,  there  is a sink  located  in  one of the
                  janitor closets  which is located  next to an electric
                  water  heater. Lessor agrees to relocate the electric water
                  heater to a safer location.

         p.       As of the Lease Commencement Date all fire sprinkler lines
                  and systems  shall  have  been  inspected  and the five
                  year test performed.  Any fire  sprinkler  lines which are
                  not  properly supported by brackets,  shall be supported in
                  accordance  with applicable building codes.

         q.       At the front of the building, there is a disconnected
                  ground wire. This shall be used or removed as necessary by
                  Lessor.

         r.       Lessee shall have no liability for the repair of the glue lam
                  beams in the building throughout the term of the Lease.

         s.       Notwithstanding  anything else  contained in this Lease to
                  the contrary,  Lessee  shall  have  no  liability  to
                  Lessor  for upgrading the building for seismic safety
                  purposes, unless the seismic  upgrade  was  required  as a
                  result  of the  specific equipment installed within the
                  Premises by Lessee.

                                      -5-
<PAGE>

PARAGRAPH 51. OPTION TO RENEW.

         Provided  Tenant is not in  material  default  under any of the
terms, covenants or condition  of this Lease,  and subject to the terms and
conditions set forth herein, Tenant is hereby granted the option to extend
this Lease for a period of three years:

         (a)      Tenant shall notify  landlord in writing of Tenant's
                  exercise of this Option to extend  this Lease on or before
                  November 1, 1999.

         (b)      The extended term of this Lease shall commence on March 1,
                  2000 and shall end on February 28, 2003 ("Extended Term").

         (c)      The  monthly   Basic  Rent  during  the  Extended  Term
                  shall increase,   annually,  in  accordance  with  the  CPI
                  formula included herein. Nevertheless,  the annual minimum
                  increase in Base  Rent  will be 2% and  the  maximum  will
                  be 4%.  The CPI formula will be as follows:

                  Consumer Price Index ("CPI") for all urban Consumers,
                  subgroup "All Items", San  Francisco-Oakland,  California
                  Metropolitan Area  (1982-84  =  100)  published  by  the
                  Bureau  of  Labor Statistics,  U.S.  Department of Labor
                  (the "Index") published nearest the first day of the month
                  twelve (12) months prior to the beginning date of the
                  Extended Term (the Beginning  Index) and the  Index  which
                  is  published  nearest  but prior to the first  day of the
                  first  Extended  Term,  and each and  every anniversary
                  date  of  the  Extended  Term  (the  "Adjustment Index").
                  The "CPI" adjusted Basic Rent shall be calculated by
                  multiplying  the Basic Rent by a fraction,  the  numerator
                  of which is the Adjustment  Index and the denominator of
                  which is the Beginning  Index.  In no event,  however,
                  shall the "CPI" adjusted Basic Rent decrease below the
                  Basic Rent of the Lease or any subsequent  adjustment
                  thereof. If the Index is changed so that the Base Year of
                  the Index  differs  from that used as of the month
                  immediately preceding the month in which the term commences
                  the Index shall be convened in  accordance  with the
                  conversion factor published by the United States Department
                  of Labor,   Bureau   of  Labor   Statistics.   If  the
                  Index  is discontinued or revised during the term, such
                  other government index or other  computation with which it
                  is replaced shall be used in order to obtain substantially
                  the same result as would be obtained if the Index had not
                  been discontinued or revised.

PARAGRAPH 52.  OPTION TO PURCHASE.

         To and  including  March 1,  1999,  Lessee  shall  have the  option
to purchase all of the Lessor's rights,  title and interest in and to the
Premises, on the following terms and conditions ("Option").

         a.       Lessor  hereby  grants  Lessee  the  Option  to  purchase
                  the Premises as set forth herein.  Attached hereto as
                  Exhibit B is a  true  and  correct  copy  of  a
                  Preliminary  Title  Report regarding the Premises issued by
                  First American Title Company. Lessee  has  approved  title
                  exceptions  ____________  of the Preliminary  Title  Report
                  and has rejected  title  exceptions _________.  Lessee
                  agrees, should it

                                      -6-
<PAGE>

                  exercise the Option granted herein, to take title subject
                  to the approved title exceptions. The disapproved title
                  exceptions shall be eliminated prior to Lessee taking title
                  to the Property.

         b.       Lessee may  exercise  this  Option only within the time
                  period set forth  above.  This right to purchase  the
                  Premises may be exercised by Lessee, or any subsidiary or
                  entity controlled by Lessee.

         c.       If Lessee has not  notified  Lessor,  in writing,  of
                  Lessee's intent to exercise this Option to Purchase, on or
                  before March 1,  1999,  then  this  Option  shall
                  automatically  terminate without any action on the part of
                  any party.

         d.       Lessee  may  exercise  this  Option,  by  notifying  Lessor
                  of Lessee's  intent,  and by  depositing  a  $10,000  check
                   into Escrow,  with the  Escrow  Holder.  The  $10,000
                  shall be the "Initial  Deposit"  into  Escrow,  and shall
                  be applied to the Purchase  Price.  The  Initial  Deposit
                  shall  be  held in an interest bearing account, for the
                  benefit of Lessee.

         e.       The Escrow Holder shall be First American Title Company.

         f.       Each party to the Escrow shall be pay its normal and customary
                  fees as is customary in San Mateo County.

         g.       Lessor shall convey the Premises to Lessee,  free of any
                  liens or encumbrances, except for those approved conditions
                  of title as set forth in Paragraph 52.A. above, Lessor
                  shall convey the Premises to Lessee in an "as is" condition.

         h.       The term of the Escrow  shall be for 120 days.  During the
                  120 days,  each party shall  submit,  to the Escrow
                  Holder,  such documents  and funds as is necessary to
                  transfer  title to the property to Lessee.  Lessee shall
                  deposit  sufficient funds to pay for the Purchase Price and
                  its share of the Closing Costs. If requested by Lessor,
                  Lessee shall cooperate with a 1031 Tax Deferred Exchange,
                  or its equivalent,  without increasing the period of the
                  time of escrow,  increasing the liability of any kind to
                  Lessee,  or  increasing  any cost to Lessee for having
                  agreed to do so.

         i.       Lessee shall have the right to purchase the Premises,  for
                  the sum of  $1,225,000  ("Purchase  Price").  j. Lessor and
                  Lessee each agree to sign any and all documents, as may be
                  reasonably required  in order to  bring  to pass the
                  contemplated  sales transaction.  Each party  agrees to act
                  in good faith and each party  shall  have all  remedies
                  available  to it,  at law or equity, in the event of a
                  breach of this Agreement.

         j.       In  the  event  Lessee  fails  to  exercise  this  Option,
                  if specifically   requested  by  Lessor,  Lessee  shall
                  execute, acknowledge and deliver to Lessor,  a quit claim
                  deed or other reasonable   document   acknowledging  that
                  this  Option  has terminated.

                                      -7-
<PAGE>

PARAGRAPH 53.

         As additional  security,  for the payment of rent due under this
Lease, Lessee agrees to tender to Lessor, a standby letter of credit in the
face amount of Seventy Nine  Thousand  Five Hundred  Sixty and No/100
Dollars . The term of this letter of credit shall be for one year. In the
event Lessee defaults in the payment  of rent for more  than 30 days,  then
Lessor  shall  have the right to receive  payment of the delinquent  rent
from the letter of credit.  The form of the letter of credit shall be
approved by Lessor and Lessee.  A letter of credit shall be issued by a bank
reasonably  acceptable  to Lessor.  The rights stated herein are in addition
to, and  cumulative,  with all of the rights and remedies that  Lessor  may
have  under law or in  equity,  and/or  under the terms of the Lease,
including without limitation the rights and remedies set out in Paragraph 13
of this Lease.

LESSORS:                                 LESSEE:
                                         DELTAGEN,
                                         a Delaware Corporation

     /s/ Martin P. Hull                  By   /s/ William Matthews
-----------------------------------         -----------------------------------
            Martin P. Hull               Its  President

     /s/ Mieke Dankers
-----------------------------------
            Mieke Dankers

     /s/ Dennis W. Royer
-----------------------------------
            Dennis W. Royer

     /s/ Christine J. Royer
-----------------------------------
            Christine J. Royer

                                      -8-<PAGE>
                                                                 Exhibit 10.5.3

                            FIRST AMENDMENT OF LEASE

         This First Amendment of Lease ("Amendment") is made and entered into as
of the 1st day of of March, 1999 by and between MARTIN P. HULL, MIEKE DANKERS,
DENNIS W. ROYER and CHRISTINE J. ROYER, tenants in common, each hereinafter
referred to as "Lessor" and DELTAGEN, a Delaware corporation ("Lessee").

                                    RECITALS

         A. Lessor and Lessee entered into a lease dated January 25, 1997
("Lease"), for the lease of the building at 1031 Bing Street, San Carlos, San
Mateo County, California ("Premises").

         B. Lessor and Lessee now desire to amend the terms of the Lease to
provide for an extension of the Lease Term.

         NOW, THEREFORE, in cosideration of the foregoing, and other good and
valuable consideration, the receipt of which is hereby acknowledged, Lessor and
Lessee agree as follows:

         1. Unless otherwise expressly provided herein, all terms which are
given a special definition by the Lease, that are used herein, are intended to
be used with the definition given to them in the Lease. The provisions of the
Lease shall remain in full force and effect except as specifically amended
hereby: In the event of any inconsistency between the Lease and this Amendment,
the terms of this Amendment shall prevail.

         2. Paragraph 1.3 is amended to extend the Lease Expiration Date by four
(4) years to the date of February 29, 2004.

         3. Paragraph 1.5 is amended to provide for the payment of the following
sums of Base Rent:

            Commencing on March 1, 1999, and continuing through the month of
February, 2004, the monthly Base Rent shall be $13,260.00.

         4. Paragraph 7.4 is amended as follows: Notwithstanding anything else
contained in the Lease to the contrary, Lessee Owned Alterations and Utility
Installations may be retained and removed from the Premises by the Lessee, at
the termination of the Lease term. Any items not removed shall become the
property of Lessor. Upon surrender of the Premises, at the Lease termination,
Lessee shall not be responsible for removal of approved Lessee Owned Alterations
or Utility Installations, nor the restoration of the Premises to its original
condition, prior to the commencement of the Lease. Nevertheless, any damage
caused by the removal of Lessee's property from the Premises shall be repaired
by Lessee. Upon surrender of the Premises, the Premises shall be clean and free
of debris and in good operating order, condition and state of repair, ordinary
wear and tear excepted.

         5. Paragraph 50(d) is replaced as follows: "Lessor and Lessee agree
that Lessor shall have no obligation to maintain HVAC units, except for the HVAC
units which were installed in the premises by January 25, 1997. However, with
respect to those units, Lessee shall bear the first $4,800 of maintenance or
repair cost each year."

         6. Paragraph 51 of the Lease is deleted in its entirety.

         7. Paragraph 52 of the Lease is deleted in its entirety.

         8. Paragraph 53 of the Lease is deleted in its entirety.

         9. Lessor agrees to pay for any and all brokerage services or fees
incurred by Lessor to obtain this Lease extension, if any, and in the event
Lessee exercises the option set forth below, for the Lease extension
resulting from the exercise of the option. Lessee shall not be obligted to
pay Lessor's real

<PAGE>

estate brokerage fees. Lessor and Lessee each agree to indemnify, defend and
hold the other party harmless from and against any and all liability, damages
and costs (including attorneys' fees) incurred by the other as a result of a
claim made by the other party's real estate broker.

         10.      Provided Lessee is not in material default under any of the
terms, covenants or conditions of this Lease, and subject to the terms and
conditions set forth herein, Lessee is herby granted the option to extend this
Lease for a period of five (5) years:

         a.       Lessee shall notify Lessor in writing of Lessee's exercise of
                  the option on or before December 1, 2003.

         b.       The extended term of this Lease shall commence on March 1,
                  2004 and shall end on February 28, 2009 ("First Extended
                  Term").

         c.       The monthly Base rent shall continue to be the monthly sum of
                  $13,260.00 throughout the First Extended term.

         11.      Except as herein modified and amended, the Lease shall remain
in full force and effect.

         IN WITNESS WHEREOF, the parties have signed this First Amendment of
Lease, which, for reference purposes, shall be deemed to have been dated as of
March 1, 1999.

Lessor:                                        Lessee:

  /s/ Martin P. Hull                           DELTAGEN, a Delaware corporation
------------------------------------
Martin P. Hull

  /s/ Mieke Dankers                     By:      /s/ William Matthews
------------------------------------           --------------------------------
Mieke Dankers                                  Its Chief Executive Officer

  /s/ Dennis W. Royers
-----------------------------------
Dennis W. Royers

  /s/ Christine J. Royers
-----------------------------------
Christine J. Royers

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