Leaf is a essential part of the plants for photosynthetic activities which mainly economize the resources for boll heath.  Significant variations of leaf shapes across the Gossypium sp. considerably influence the infiltration of sunlight for photosynthesis.  To understand the genetic variants and molecular processes underlying for cotton leaf shape, we used F₂ population derived from upland cotton genotype P30A (shallow-lobed leaf) and sea-island cotton genotype ISR (deep-lobed leaf) to map leaf deep lobed phenotype controlling genes LBL1 and LBL2.  Genetic analysis and localization results have unmasked the position and interaction between both loci of LBL1 and LBL2, and revealed the co-dominance impact of the genes in regulating depth of leaf blades lobes in cotton.  LBL1 had been described as a main gene and member of transcription factor family leucine zipper (HD-ZIPI) from a class I homologous domain factor Gorai.002G244000.  The qRT-PCR results elaborated the continuous change in expression level of LBL1 at different growth stages and leaf parts of cotton.  Higher expression level was observed in mature large leaves followed by medium and young leaves respectively.  For further confirmation, plants were tested from hormonal induction treatments, which explained that LBL1 expression was influenced by hormonal signaling.  Moreover, the highest expression level was detected in brassinolides (BR) treatment as compared to other hormones, and this hormone plays an important role in the process of leaf blade lobed formation.