Mariano Isaac Abella was one of the 94 signatories of the Malolos Constitution, which established the first Philippine Republic. He served as Governor of Ambos Camarines (what is now know today as Camarines Norte and Camarines Sur) for three terms (1898, 1904, and 1907). As a businessman, he actively participated in the management of his family's significant land holdings (the largest producer of abaca at the time) and also held the Congressional utilities franchise to install, operate, and maintain the electrical power grid in Bicol. Mariano was born on September 26, 1860, in Nueva Caceres, Ambos Camarines, Philippines. He was the eldest child of Manuel Pinzon Abella and Bibiana Isaac.

Mariano spent his early years in his hometown, where he studied at the local seminary. The 12-year-old Mariano was then sent to study at the Colegio de San Juan de Letran in Manila, where he received his Bachillerato in 1879.^[1] He went on to pursue a law degree, but had to put this on hold to tend to the families agricultural interests. After four years, he resumed his law studies and finished his law degree at the University of Santo Tomas in 1889.^[1] Like many of his university contemporaries, he embarked for Spain in 1890, to see the world and to fuel his Reformist leanings. From Spain, he travelled to France, Belgium, Germany and Italy and stayed abroad for 4 years. He returned to the Philippines on April 27, 1894, on board the ship Montevideo, accompanied by the brothers Juan Luna and Antonio Luna.^[1]

Mariano returned to his hometown and built a successful law practice. In time, he became a justice of the peace and a judge of the Court of First Instance. He married Juana Hernandez Imperial, and their union was blessed with two children: Manuel and Socorro.^[1]

At the heels of the Philippine Revolution, the Bicol region felt the brunt of the Spanish colonial government's campaigns to crush the revolution. Suspected of rebellion against Spain, Mariano was arrested and imprisoned in Bilibid Prison on 16 September 1896, before the Cry of Pugad Lawin; while his father and brothers were taken a few days later. He was set free by the Spanish court in the summary trial on 29 December 1896. His father Manuel and brother Domingo were executed in Bagumbayan; while his brother Ramon was exiled to Fernando Po Island in Africa.

His family's tragedies fueled Mariano's fervor to reform government. As the representative of Ambos Camarines to the Malolos Congress, Manuel was one of the 94 signatories of the Malolos Constitution, which established the First Philippine Republic.^[2] He served as the governor of Ambos Camarines (the area known today as Camarines Norte and Camarines Sur) for three terms: 1898, 1904, and 1907, after which he retired from politics to manage his family's business interests.

As a businessman, he actively participated in the management of his family's land. He also held the Congressional franchise to install, operate and maintain the electric power system in various towns in Bicol.^[3][4]