<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D. C. 20549
                           --------------------------

                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       The Securities Exchange Act of 1934
                            -------------------------

        Date of Report (Date of earliest event reported): August 15, 2005

                          MERRILL LYNCH DEPOSITOR, INC.
                     (ON BEHALF OF PPLUS TRUST SERIES GSG-1)
             (Exact name of registrant as specified in its charter)

              DELAWARE             001-31604                    13-3891329
          (State or other        (Commission                (I. R. S. Employer
          jurisdiction  of        File Number)              Identification No.)
           incorporation)

       WORLD FINANCIAL CENTER,                                     10080
         NEW YORK, NEW YORK                                     (Zip Code)
        (Address of principal
         executive offices)
                           --------------------------

       Registrant's telephone number, including area code: (212) 449-1000

                      INFORMATION TO BE INCLUDED IN REPORT


SECTION 1.   REGISTRANT'S BUSINESS AND OPERATIONS

             Not applicable.

SECTION 2.   FINANCIAL INFORMATION

             Not applicable.

SECTION 3.   SECURITIES AND TRADING MARKETS

             Not applicable.

SECTION 4.   MATTERS RELATED TO ACCOUNTANTS AND FINANCIAL STATEMENTS

             Not applicable.

SECTION 5.   CORPORATE GOVERNANCE AND MANAGEMENT

             Not applicable.


<PAGE>

SECTION 6.   [RESERVED]

SECTION 7.   REGULATION FD

             Not applicable.

SECTION 8.   OTHER EVENTS

  ITEM 8.01  OTHER EVENTS

       99.1  Distribution to holders of the PPLUS Trust Certificates Series
             GSG-1 on August 15, 2005.

                    For information with respect to the underlying securities
             held by PPLUS Trust Series GSG-1, please refer to The Goldman Sachs
             Group, Inc.'s (Commission file number 001-14965) periodic reports,
             including annual reports on Form 10-K, quarterly reports on Form
             10-Q and current reports on Form 8-K, and other information on file
             with the Securities and Exchange Commission (the "SEC"). You can
             read and copy these reports and other information at the public
             reference facilities maintained by the SEC at Room 1580, 100 F
             Street, NE, Washington, D.C. 20549. You may obtain copies of this
             material for a fee by writing to the SEC's Public Reference Section
             of the SEC at 100 F Street, NE, Washington, D.C. 20549. You may
             obtain information about the operation of the Public Reference Room
             by calling the SEC at 1-800-SEC-0330. You can also access some of
             this information electronically by means of the SEC's website on
             the Internet at http://www.sec.gov, which contains reports, proxy
             and information statements and other information that the
             underlying securities issuer has filed electronically with the SEC.

                    Although we have no reason to believe the information
             concerning the underlying securities or the underlying securities
             issuer contained in the underlying securities issuer's Exchange Act
             reports is not reliable, neither the depositor nor the trustee
             participated in the preparation of such documents or made any due
             diligence inquiry with respect to the information provided therein.
             No investigation with respect to the underlying securities issuer
             (including, without limitation, no investigation as to its
             financial condition or creditworthiness) or of the underlying
             securities has been made. You should obtain and evaluate the same
             information concerning the underlying securities issuer as you
             would obtain and evaluate if your investment were directly in the
             underlying securities or in other securities issued by the
             underlying securities issuer. There can be no assurance that events
             affecting the underlying securities or the underlying securities
             issuer have not occurred or have not yet been publicly disclosed
             which would affect the accuracy or completeness of the publicly
             available documents described above.



<PAGE>


SECTION 9.   FINANCIAL STATEMENTS AND EXHIBITS

  ITEM 9.01  FINANCIAL STATEMENTS AND EXHIBITS


             (a) Financial statements of business acquired.

                 Not Applicable.

             (b) Pro forma financial information.

                 Not Applicable.

             (c) Exhibits.

                 99.1  Trustee's report in respect of the August 15, 2005
                       distribution to holders of the PPLUS Trust Certificates
                       Series GSG-1.



<PAGE>

                                   SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, hereunto duly authorized.


                                            MERRILL LYNCH DEPOSITOR, INC.

Date: August 25, 2005                       By:    /s/ Stephan Kuppenheimer
                                                   -----------------------------
                                            Name:  Stephan Kuppenheimer
                                            Title: President








<PAGE>

                                  EXHIBIT INDEX


99.1     Trustee's report in respect of the August 15, 2005 distribution to
         holders of the PPLUS Trust Certificates Series GSG-1.
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SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D. C. 20549
                           --------------------------

                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       The Securities Exchange Act of 1934
                            -------------------------

        Date of Report (Date of earliest event reported): August 15, 2005

                          MERRILL LYNCH DEPOSITOR, INC.
                     (ON BEHALF OF PPLUS TRUST SERIES GSG-1)
             (Exact name of registrant as specified in its charter)

              DELAWARE             001-31604                    13-3891329
          (State or other        (Commission                (I. R. S. Employer
          jurisdiction  of        File Number)              Identification No.)
           incorporation)

       WORLD FINANCIAL CENTER,                                     10080
         NEW YORK, NEW YORK                                     (Zip Code)
        (Address of principal
         executive offices)
                           --------------------------

       Registrant's telephone number, including area code: (212) 449-1000

                      INFORMATION TO BE INCLUDED IN REPORT

SECTION 1.   REGISTRANT'S BUSINESS AND OPERATIONS

             Not applicable.

SECTION 2.   FINANCIAL INFORMATION

             Not applicable.

SECTION 3.   SECURITIES AND TRADING MARKETS

             Not applicable.

SECTION 4.   MATTERS RELATED TO ACCOUNTANTS AND FINANCIAL STATEMENTS

             Not applicable.

SECTION 5.   CORPORATE GOVERNANCE AND MANAGEMENT

             Not applicable.
SECTION 6.   [RESERVED]

SECTION 7.   REGULATION FD

             Not applicable.

SECTION 8.   OTHER EVENTS

  ITEM 8.01  OTHER EVENTS

       99.1  Distribution to holders of the PPLUS Trust Certificates Series
             GSG-1 on August 15, 2005.

                    For information with respect to the underlying securities
             held by PPLUS Trust Series GSG-1, please refer to The Goldman Sachs
             Group, Inc.'s (Commission file number 001-14965) periodic reports,
             including annual reports on Form 10-K, quarterly reports on Form
             10-Q and current reports on Form 8-K, and other information on file
             with the Securities and Exchange Commission (the "SEC"). You can
             read and copy these reports and other information at the public
             reference facilities maintained by the SEC at Room 1580, 100 F
             Street, NE, Washington, D.C. 20549. You may obtain copies of this
             material for a fee by writing to the SEC's Public Reference Section
             of the SEC at 100 F Street, NE, Washington, D.C. 20549. You may
             obtain information about the operation of the Public Reference Room
             by calling the SEC at 1-800-SEC-0330. You can also access some of
             this information electronically by means of the SEC's website on
             the Internet at http://www.sec.gov, which contains reports, proxy
             and information statements and other information that the
             underlying securities issuer has filed electronically with the SEC.

                    Although we have no reason to believe the information
             concerning the underlying securities or the underlying securities
             issuer contained in the underlying securities issuer's Exchange Act
             reports is not reliable, neither the depositor nor the trustee
             participated in the preparation of such documents or made any due
             diligence inquiry with respect to the information provided therein.
             No investigation with respect to the underlying securities issuer
             (including, without limitation, no investigation as to its
             financial condition or creditworthiness) or of the underlying
             securities has been made. You should obtain and evaluate the same
             information concerning the underlying securities issuer as you
             would obtain and evaluate if your investment were directly in the
             underlying securities or in other securities issued by the
             underlying securities issuer. There can be no assurance that events
             affecting the underlying securities or the underlying securities
             issuer have not occurred or have not yet been publicly disclosed
             which would affect the accuracy or completeness of the publicly
             available documents described above.
SECTION 9.   FINANCIAL STATEMENTS AND EXHIBITS

  ITEM 9.01  FINANCIAL STATEMENTS AND EXHIBITS

             (a) Financial statements of business acquired.

                 Not Applicable.

             (b) Pro forma financial information.

                 Not Applicable.

             (c) Exhibits.

                 99.1  Trustee's report in respect of the August 15, 2005
                       distribution to holders of the PPLUS Trust Certificates
                       Series GSG-1.
SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, hereunto duly authorized.

                                            MERRILL LYNCH DEPOSITOR, INC.

Date: August 25, 2005                       By:    /s/ Stephan Kuppenheimer
                                                   -----------------------------
                                            Name:  Stephan Kuppenheimer
                                            Title: President
EXHIBIT INDEX

99.1     Trustee's report in respect of the August 15, 2005 distribution to
         holders of the PPLUS Trust Certificates Series GSG-1.