Reivindicaciones

1. A recombinant DNA molecule comprising the DNA sequence of the AtBIP3 promoter (pAtBIP3) (SEQ ID NO: 1) and the DNA sequence coding for the Arabidopsis HOP3 protein, AtHOP3 (SEQ ID NO: 2), wherein expression of protein AtHOP3 is under the control of the AtBiP3 promoter. 2. Method of obtention of the recombinant DNA molecule of claim 1. 3. Use of AtHOP3 expression under the AtBiP3 promoter to promote seed germination and seedling establishment rate and improve fruit quality and ripening in plants under stress conditions. 4. The use of claim 3 wherein the stress conditions consist in high salt conditions. 5. A transgenic plant, or part thereof, comprising the genetic construct pAtBIP3:AtHOP3. 6. The transgenic plant, or part thereof, of claim 5 wherein said transgenic plant is a monocotyledonous plant or a dicotyledonous plant. 7. The transgenic plant, or part thereof, of claim 6 wherein the plant belongs to the Arabidopsis thaliana sp. or is Solanum lycopersicum. 8. Method of producing the transgenic plant, or part thereof, of claims 5 to 7, by transforming plants with the genetic construct pAtBIP3:AtHOP3. 9. The method of claim 8 wherein the transgenic plan is Arabidopsis thaliana sp and the transformation method is the floral dip method, wherein transgenic seeds are generated that further generate transgenic plants directly. 10. The method of claim 8 wherein the transgenic plan is Solanum lycopersicum and the transformation method consists on transformation of cotyledon explants, wherein transformed cells form callus are used to regenerate whole transgenic plants. 11. Use of the transgenic plant, or part thereof, of claims 5 to 7, in crops subjected to environmental stress conditions or any other condition that courses with ER stress or a combination of them. 12. The use of claim 11 wherein the environmental stress conditions are selected from high salt stress conditions, pest and pathogen infections, high temperatures and drought.