Fuente: WIPO "tomato" Methods and compositions for enhancing heterologous protein expression in plants are provided. The invention is directed to the co-expression of a heterologous protein of interest with a specific endoplasmic reticulum (ER)-resident molecular chaperone protein. Co-expressing chaperones such as a native soybean protein disulfide isomerase-like protein (Glyma.01G003700, Glyma.04g247900, Glyma.03G218300, or Glyma.18G204000), or a heterologous mammalian chaperone (bovine DNAJB12) with casein proteins in soybean cells resulted in a significant increase in casein accumulation, with up to 4-fold enhancement observed. The methods are broadly applicable for improving the yield of complex recombinant proteins, including milk proteins, therapeutic proteins, and industrial enzymes, in plant-based production systems, thereby overcoming common limitations related to protein folding and stability.