Functional redundancy of <i>OsPIN1</i> paralogous genes in regulating plant growth and development in rice

The <i>OsPIN1</i> paralogous genes (<i>OsPIN1a-1d</i>) are important for root and panicle development in rice (<i>Oryza sativa</i> L.). However, the specific role of <i>OsPIN1</i> paralogous genes is still not clear. To understand the specific roles of <i>PIN1</i> paralogs in rice, we generated <i>pin1</i> triple and quadruple mutants by crossing the <i>pin1a pin1b</i> and <i>pin1c pin1d</i> double mutants which we previously created. Compared with the 7-day-old wild type, the <i>pin1a pin1c pin1d</i> and <i>pin1b pin1c pin1d</i> triple mutants showed no obvious phenotype variation except that the <i>pin1a pin1c pin1d</i> triple mutant had shorter primary root and shoot. The <i>pin1a pin1b pin1c</i> and <i>pin1a pin1b pin1d</i> triple mutants exhibited a series of developmental abnormalities, including shorter primary roots, longer root hairs, fewer crown roots and lateral roots, shorter and curved shoots. Furthermore, the <i>pin1a pin1b pin1c pin1d</i> quadruple mutant displayed more severe phenotypic defects which was lethal. In addition, the expression levels of some hormone signal transduction and crown root development related genes, such as <i>OsIAAs, OsARFs, OsRRs</i>, and <i>OsCRLs</i>, were significantly altered in the stem base of all examined <i>pin1</i> multiple mutants. Taken together, our results demonstrated that the four <i>OsPIN1</i> paralogous genes function redundantly in regulating rice growth and development.