N-terminal HrpE from Xanthomonas Oryzae Pv. Oryzae Mediates the Regulation of Growth and Photosynthesis in Rice

Harpin proteins, produced by gram-negative bacteria, can enhance the plant growth. The growth enhancing potential of the harpins are beneficial and may be associated with the functional regions of the proteins. Harpins are also known to stimulate the hypersensitive cell death (HCD) but identification of functional terminal of the proteins may be beneficial to use the deleterious regions of these proteins without any negative effects like HCD. Here, we report the identification and testing of the derivate fragments of HrpE protein from Xanthomonas oryzae pv. oryzae, the pathogen that causes the bacterial blight disease in rice. Two fragments of the HrpE protein i.e. C-HrpE and N-HrpE generated by truncation mutation were evaluated for their response on the seed vigor index and vegetative growth of the rice plants. Rice seedlings and plants evaluated for their root and shoot morphology showed that N-HrpE protein is essential for plant growth enhancement and increased photosynthetic efficiency. Rice plants grown under the influence of HrpE and its derivate fragments were evaluated for the transcriptional profiling of the genes related to the plant growth and quantification of the growth regulatory hormones by UPLC provides the necessary avenues to prove that HrpE requires N terminus to enhance the vegetative growth in rice.