RNA Interference-Mediated Suppression of GhSP (SELF-PRUNING) Modulates the Plant Architecture of Transgenic Cotton in a Dose-Dependent Manner

Cotton exhibits indeterminate growth potential at its apical meristem. In field cultivation, it is often necessary to restrict plant height by the foliar application of plant growth regulators or artificial topping. The genetic engineering of cotton architecture offers an efficient, environmentally friendly, and low-cost alternative to current field management. Our study aimed to improve the plant architecture of transgenic cotton by the suppression of <i>GhSP</i>, a key flowering repressor, via the RNA interference method. Sixteen independent transgenic lines were generated and classified as mildly, moderately, and severely suppressed, according to <i>GhSP</i> expression levels. Field evaluation revealed the dose-dependent effects of <i>GhSP</i> silencing on plant height. The mildly suppressed line <i>GhSPi</i>-#5 exhibited a semi-dwarf phenotype of approximately 70~100 cm in height. Negative phenotypes, including excessive dwarf plant architecture and inferior fiber quality and yield traits, were observed in severely <i>GhSP</i>-suppressed transgenic lines. Notably, the mild silencing of <i>GhSP</i> in <i>GhSPi</i>-#5 did not negatively affect leaf and flower organ growth, pollen fertility, major agronomic traits, or fiber quality compared with the wild type. These observations demonstrate the feasibility of manipulating the architecture of transgenic cotton via <i>GhSP</i> silencing.