Nitric Oxide Modulates the Expression of Aquaporin Isoforms (PIP2 and TIP1) on Oil Body Membranes in Sunflower ( Helianthus Annuus L.) Seedling Cotyledons in Response to Salt Stress

High salt content in soil restricts the growth and development of agricultural crops, limiting their yield. Aquaporins (AQP) are specialized organelles responsible for precise regulation of water movement across the membranes. Experimental analysis of multigenic defense approaches for acclimatization against salt stress has shown that nitric oxide (NO) and AQP may play a crucial role in overcoming salt stress during early stages of seedling growth in oilseeds, such as sunflower. Present work demonstrates the variation in the abundance of AQPs [Plasma membrane Intrinsic Protein 2 (PIP2) and Tonoplast Intrinsic Protein 1 (TIP1)] in whole tissue homogenates of 2 d old, dark-grown, sunflower seedling cotyledons, in response to salt stress. Enhanced expression of PIP2 and TIP1 in cotyledons of seedlings raised in the presence of 120 mM NaCl suggests a link of these AQP isoforms with salt stress acclimatization, possibly through protection against osmotic stress. NO application leads to expression of dimeric forms of both PIP isoforms (PIP1 and PIP2). Present work also reports accumulation of four aquaporin isoforms (PIP1 and PIP2; TIP1 and TIP2) on the oil body (OB) membrane. A molecular crosstalk between NO and expression of specific AQP isoforms thus appears to regulate the hydration status of oilseed cotyledons in seedlings facing salt stress.