<PAGE>


                                                                 EXHIBIT 10.52


                              CONSULTING AGREEMENT


     This Consulting Agreement ("Agreement") is entered into by and between
William Matthews, Ph.D. ("Matthews") and Deltagen, Inc., a Delaware corporation
("Deltagen") (together the "Parties") as of the Effective Date of the Transition
Agreement and Release by and between Matthews and Deltagen, dated January 17,
2003 (the "Transition Agreement and Release").


                                    RECITALS

     Matthews' employment as Chief Executive Officer ("CEO") of Deltagen has
terminated on the Separation Date pursuant to Section 1(a) of the Transition
Agreement and Release, and Deltagen desires, subject to the terms hereof, to
retain Matthews' services to assist in the transition of his duties as CEO and
to assist in the defense of certain actions now pending and certain actions
which may be brought in the future by any third party against Deltagen and to
provide such other consulting services as may be reasonably requested by the
Deltagen's Board of Directors or its Chief Executive Officer.

     1. Consulting Services.

     Pursuant to this Agreement:

               (a)  Matthews shall assist Deltagen (i) in all matters relating
to the winding up of work pending at the time of his separation from Deltagen
and the orderly transfer of Matthews' prior responsibilities to other person(s)
for a total of up to ninety (90) days (or the equivalent thereof in working
hours) ("Transition Services"), (b) in the vigorous defense of any action
brought by any third party against Deltagen or its affiliates that relates in
any way to Matthews' acts or omissions while he was employed by Deltagen or in
the vigorous defense of any action brought by any third party relating to
litigation or claims pending against Deltagen or its affiliates at the time of
his separation from Deltagen ("Litigation Services") and (c) any other
consulting services reasonably requested during the term of this Agreement by
Deltagen's Board of Directors or its Chief Executive Officer ("Consulting
Services," collectively with Transition Services and Litigation Services, the
"Services"). The Transition Services to be provided shall include, but not be
limited to, meeting with Deltagen's executive staff as needed to discuss pending
work and the on-going responsibilities of the Chief Executive Officer position.
The Litigation Services shall include, but not be limited to: (i) affirmatively
and appropriately assisting Deltagen and its counsel in the defense of any
action brought against Deltagen or its affiliates; (ii) meeting with Deltagen's
counsel as needed to discuss any pending litigation or claims; (iii) being
available for depositions at his and Deltagen's convenience; and (iv) if
necessary, testifying at trial. Matthews agrees to perform the Services with the
standard of care, skill and diligence normally provided by a professional person
in the performance of similar services.

               (b)  Deltagen shall own all rights to any and all work products,
patents, processes, copyrights, studies, flow charts, diagrams, devices,
programs, source codes, inventions, original works of authorship, know-how, and
other tangible or intangible material or data of any nature developed by
Matthews or as a result of any of Matthews' Services. Any

                                       1

<PAGE>

work product generated by Matthews hereunder shall be deemed a work made for
hire. If any of such work product shall be deemed other than a work for hire,
Matthews hereby assigns to Deltagen all rights, title and interest in and to
such work product, Matthews agrees to execute and deliver such documents and
instruments as Deltagen may deem necessary and appropriate to transfer to
Deltagen any and all rights, title, and interest, including copyrights, Matthews
has in any such work.

               (c)  Matthews agrees that during the term of the Agreement, and
for a period of twelve months immediately following the termination of the
Agreement for any reason, Matthews shall not either directly or indirectly
solicit, induce, recruit or encourage any of Deltagen's or its affiliates'
employees or other consultants to terminate their relationship with Deltagen or
its affiliates, or take away such employees or consultants, or attempt to
solicit, induce, recruit, encourage or take away employees or consultants of
Deltagen or its affiliates, either for himself or for any other person or
entity. Moreover, during the term of this Agreement, and for a period of twelve
months immediately following the termination of this Agreement, Matthews shall
not become an employee or officer or director of (or provide consulting or
advisory services to) any company, entity, venture or business that competes
with Deltagen or its affiliates. For the purposes of this Agreement, a company
shall be deemed to compete with Deltagen if a significant focus or purpose of
its business is to provide mouse transgenics services to a third party in any
form, including without limitation on a fee-for-service or collaborative basis.
Further, for a period of twelve months following termination of this Agreement
for any reason, Matthews shall not solicit any licensor to or customer of
Deltagen or its affiliates or licensee of Deltagen's or its affiliates'
products, in each case, that are known to Matthews, with respect to any
business, products or services that are competitive to the products or services
offered by Deltagen or its affiliates or under development as of the date of
termination of the Agreement.

     2.   Compensation. For Services performed by Matthews under this Agreement,
during the term of this Agreement, Deltagen shall pay Matthews on a monthly
basis (paid in arrears) at an annual rate of $[225,000]. In addition,
Executive's stock options may continue to vest and be exercisable, pursuant to
the option grant terms, while Executive provides consulting services to the
Company pursuant to this Agreement.

     3.   Expenses. Deltagen agrees to reimburse Matthews for all expenses
reasonably incurred in the performance of the Services upon production of
supporting receipts and documentation and where such expenses have been
pre-authorized by Deltagen. Matthews shall invoice Deltagen on a monthly basis
for any expenses reasonably incurred in the performance of the Services.
Deltagen shall pay all invoices within forty-five (45) days after their receipt.

     4.   Term Of Agreement. This Agreement shall become effective upon
Matthews' Separation Date and will remain in effect until the first anniversary
of the Separation Date provided, however, Matthews shall continue to be
available to provide Litigation Services for any litigation against Deltagen or
its affiliates that is (i) pending at the time of Matthews' termination of
employment with Deltagen, or (ii) involves events and circumstances occurring
during Matthews' employment with Deltagen regardless of when the litigation is
initiated ("Consultancy Period"). This Agreement shall also terminate
immediately upon Matthews' death or if Matthews revokes the release of claims
described in Section 6(b) of the Transition

                                       2

<PAGE>

Agreement and Release and shall be terminable by Deltagen for "Disability"
(which for purposes of this Agreement shall mean Matthews' inability to perform
the Services) or upon Matthews' material breach of either this Agreement
(including, without limitation, Matthews' refusal, or substantial failure, to
perform the services contemplated by this Agreement) or the Transition Agreement
and Release. Upon termination of this Agreement, Matthews shall be entitled to
payment for unpaid amounts for Services completed, and for reimbursement for
expenses incurred, during the Consultancy Period. Thereafter, Deltagen shall owe
Matthews no further amounts or obligations under this Agreement.

     5.   Notices. Any notice or other communication under this Agreement must
be in writing and shall be effective upon delivery by hand, upon facsimile
transmission to either party or three (3) business days after deposit in the
United States mail, postage prepaid, certified or registered, and addressed to
Deltagen or to Matthews at the corresponding address or fax number (if any)
below. Matthews shall be obligated to notify Deltagen in writing of any change
in his address. Notice of change of address shall be effective only when done in
accordance with this Section 5.

Deltagen's Notice Address:

     740 Bay Road
     Redwood City, CA 94063
     Fax Number:  650-569-5280

Matthews' Notice Address:

     William Matthews, Ph.D.
     60 Summit Springs Road
     Woodside, CA 94062
     Fax Number:

     6.   Relationship Of The Parties.

               (a)  Matthews enters into this Agreement as, and shall continue
to be, an independent contractor throughout the Consultancy Period. In no
circumstance shall Matthews look to Deltagen or its affiliates as Matthews'
employer during the term of this Agreement. Except as may be otherwise stated in
the Transition Agreement and Release, Matthews shall not be entitled to any
benefits accorded to Deltagen's or its affiliates' employees, including workers'
compensation, disability insurance, retirement plans, or vacation or sick pay.
Matthews' exclusion from benefit programs maintained by Deltagen or its
affiliates during the Consultancy Period is a material component of the terms of
compensation negotiated by the Parties, and is not premised on Matthews' status
as a non-employee with respect to Deltagen or its affiliates. To the extent that
Matthews may become eligible for any benefit programs maintained by Deltagen or
its affiliates (regardless of the timing of or reason for eligibility) during
the Consultancy Period, Matthews hereby waives Matthews' right to participate in
the programs. Matthews' waiver is not conditioned on any representation or
assumption concerning Matthews' status under the common law test. Matthews also
agrees that, consistent with Matthews' independent

                                       3

<PAGE>

contractor status, Matthews will not apply for any government-sponsored benefits
that are intended to apply to employees, including, but not limited to,
unemployment benefits.

               (b)  Matthews shall be responsible for providing, at Matthews'
expense and in Matthews' name, to the extent applicable, disability, workers'
compensation, or other insurance as well as licenses and permits usual or
necessary for performing the Services. Matthews shall pay, when and as due, any
and all taxes incurred as a result of Matthews' compensation, including
estimated taxes and payroll taxes, and shall provide Deltagen with proof of
payment as may be requested under Section 6(c) below.

               (c)  Matthews and Deltagen shall provide to each other upon
request any information reasonably necessary to determine their obligations
under this Agreement, to fulfill the purposes of the Services, or to maintain
accurate records.

     7.   Privileged and Confidential Information.

     (a)  Matthews acknowledges and understands that, in assisting Deltagen with
the defense of actions under this Agreement, the Parties intend the attorney
client privilege and/or attorney-work product to apply to the fullest extent
permitted by law ("Privileged Information"). Matthews agrees to hold all
Privileged Information in confidence and shall not disclose any Privileged
Information to any third-party except at the direction of Deltagen's counsel.
Deltagen agrees to provide legal representation, at no cost to Matthews, for any
assistance requested by Deltagen and provided by Matthews under this Agreement.

     (b)  Matthews shall not publish, disclose, or otherwise divulge
Confidential Information to any person, at any time during or after the term of
this Agreement, without Deltagen's prior express written consent. For purposes
of this Agreement, "Confidential Information" shall mean non-public,
confidential or proprietary information belonging to Deltagen or its affiliates.

     The term "Confidential Information" does not include any information which
(i) at the time of disclosure or thereafter is generally available to the public
(other than as a result of a disclosure by Matthews or her representatives in
violation of this Agreement), (ii) was available to Matthews on a
non-confidential basis from a source other than Deltagen, provided that such
source is not bound by a confidentiality agreement that was applicable to the
Confidential Information, or (iii) has been independently acquired or developed
by Matthews without violating any of his obligations under this Agreement.

     In the event that Matthews becomes legally compelled (by deposition,
interrogatory, request for documents, subpoena, civil investigative demand or
other similar legal process) to disclose any of the Confidential Information,
Matthews shall give Deltagen prompt prior written notice of such requirement so
that Deltagen may seek a protective order or other appropriate remedy and/or
waive compliance with the terms of this Agreement. In the event that such
protective order or other remedy is not obtained, or that Deltagen waives
compliance with the terms hereof, Matthews agrees to provide only that limited
portion of the Confidential Information that it is advised by written opinion of
counsel is legally required and to exercise

                                       4

<PAGE>

reasonable efforts to obtain assurance that confidential treatment will be
accorded such Confidential Information.

     Matthews represents that his performance of all terms of this Agreement as
a consultant of Deltagen has not breached and will not breach any agreement to
keep in confidence proprietary information, knowledge or data acquired by
Matthews in confidence or trust prior or subsequent to the commencement of the
Agreement, and Matthews will not disclose to Deltagen or its affiliates, or
induce Deltagen or its affiliates to use, any inventions, confidential or
proprietary information or material belonging to any previous employer or any
other party.

     The Parties agree that in the event of a breach of this Confidentiality
provision, Deltagen shall be entitled to equitable relief, including injunction
and specific performance, in addition to all other remedies available at law or
equity.

     8.   Arbitration; Attorney's Fees. To the fullest extent permitted by law,
subject to Section 10(c) of the Transition and Release Agreement, all claims
that Matthews may have against Deltagen, or which Deltagen may have against
Matthews in any way related to the subject matter, interpretation, application,
or alleged breach of this Agreement shall be resolved by arbitration as set
forth in Section 10 of the Transition Agreement and Release. The provisions of
Section 12 of the Transition Agreement and Release shall apply to this Agreement
as set forth in the Transition Agreement and Release.

     9.   Integration. The parties understand and agree that this Agreement
represents the entire Agreement as to the matters discussed in this Agreement,
except as otherwise referenced in the Transition Agreement and Release. There
has been no representation or promise made by Matthews or Deltagen on any
subject discussed in this Agreement, except as expressly set forth in the
Transition Agreement and Release. This Agreement shall supersede all prior or
contemporaneous agreements and understandings among Matthews and Deltagen,
whether written or oral, express or implied, with respect to any subject under
this Agreement, except as has otherwise provided in the Transition Agreement and
Release.

     10.  Amendments; Waivers. This Agreement may not be amended except by an
instrument in writing, signed by each of the Parties. No failure to exercise and
no delay in exercising any right, remedy, or power under this Agreement shall
operate as a waiver thereof, nor shall any single or partial exercise of any
right, remedy, or power under this Agreement preclude any other or further
exercise thereof, or the exercise of any other right, remedy, or power provided
herein or by law or in equity.

     11.  Assignment; Successors and Assigns. Matthews agrees that he will not
assign, sell, transfer, delegate, or otherwise dispose of, whether voluntarily
or involuntarily, or by operation of law, any rights or obligations under this
Agreement. Any such purported assignment, transfer, or delegation prohibited
hereunder shall be null and void. In the event of Matthews' death, payments due
and arising hereunder shall be made to Matthews' estate, designee(s) or legal
heirs and assigns. Matthews represents that he has not previously assigned or
transferred any claims or rights released, or purported to be released, by him
pursuant to this Agreement. Deltagen shall not assign or transfer its rights and
obligations hereunder except to a successor to all or substantially all of the
assets of Deltagen, whether by merger, consolidation, transfer of assets or

                                       5

<PAGE>

otherwise so long as such successor assumes Deltagen's obligations hereunder.
Subject to the foregoing, this Agreement shall be binding upon and shall inure
to the benefit of the Parties and their respective heirs, successors,
affiliates, attorneys, and permitted assigns. This Agreement shall not benefit
any other person or entity except as specifically enumerated in this Agreement
and their permitted heirs, successors, affiliates and assigns.

     12.  Severability. If any provision of this Agreement, or its application
to any person, place, or circumstance, is held by an arbitrator or a court of
competent jurisdiction to be invalid, unenforceable, or void, such provision
shall be enforced to the greatest extent permitted by law, and the remainder of
this Agreement and such provision as applied to other persons, places, and
circumstances shall remain in full force and effect.

     13.  Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of California.

     14.  Interpretation. This Agreement shall be construed as a whole,
according to its fair meaning, and not in favor of or against any party. By way
of example and not in limitation, this Agreement shall not be construed in favor
of the party receiving a benefit or against the party responsible for any
particular language in this Agreement. Captions are used for reference purposes
only and should be ignored in the interpretation of the Agreement.

     15.  Representation by Counsel. The Parties acknowledge that (i) they have
had the opportunity to consult counsel in regard to this Agreement; (ii) they
have read and understand the Agreement and they are fully aware of its legal
effect; and (iii) they are entering into this Agreement freely and voluntarily,
and based on each party's own judgment and not on any representations or
promises made by the other party, other than those contained in this Agreement
and the Transition Agreement and Release.

     The Parties have duly executed this Agreement as of the date first written
above.

DELTAGEN, INC.                          WILLIAM MATTHEWS, PH.D.



By: _________________________________   ________________________________________



Title:

                                       6