$a=2Y_{\xi}u_{\xi}$ and $b=2Y_{N}u$. Hence the light neutrino mass matrix, using the type I seesaw formula is $$-M_{\nu}= M^0_D M^{-1}_{R} {M^0}_D^T= v^2_2 Y^2_{\nu 1} \left(\begin{array}{ccc}
\frac{3a+b}{3(a+b)} & \frac{b}{3(a+b)} & \frac{b}{3(a+b)} \\
\frac{b}{3(a+b)} & \frac{-b(2a+b)}{3(a+b)(a-b)} & \frac{3a^2+ab-b^2}{3(a+b)(a-b)} \\
\frac{b}{3(a+b)} & \frac{3a^2+ab-b^2}{3(a+b)(a-b)} & \frac{-b(2a+b}{3(a+b)(a-b)}
\end{array}\right). 
\label{mlight1}$$ This $\mu-\tau$ symmetric light neutrino mass matrix can be diagonalised by the usual tri-bimaximal mixing matrix given by [@Harrison:2002er] $$U_{\rm TBM}=\left(\begin{array}{ccc}
\sqrt{\frac{2}{3}} & \frac{1}{\sqrt{3}} & 0 \\
\frac{-1}{\sqrt{6}} & \frac{1}{\sqrt{3}} &\frac{-1}{\sqrt{2}} \\
\frac{-1}{\sqrt{6}} & \frac{1}{\sqrt{3}} &\frac{1}{\sqrt{2}}
\end{array}\right),
\label{utb}$$ predicting $\theta_{13}=0$ and maximal value of $\theta_{23}$. Present experimental observation, however, rules out $\theta_{13}=0$ scenario and has a preference towards higher octant for $\theta_{23}$ ($i.e. \theta_{23}>45^{\circ}$) [@Esteban:2018azc]. We therefore consider the Planck scale suppressed corrections to such scenarios so that the correct light neutrino phenomenology can be obtained along with the implications for dark sector.

The contribution to the light neutrino mass matrix and neutrino mixing from the Planck suppressed terms which break the discrete symmetries explicitly can arise in a variety of ways. For example,

-   there can be contributions to light neutrino mass matrix of the type $(L L H H)/M_{\rm Pl}, (L L H_T H_T)/M_{\rm Pl}, (L L H_T H)/M_{\rm Pl}$, all of which remain at 