Phytosulfokine (PSK) is a newly discovered plant hormone, which can promote cell division and induce cell differentiation. It has 7 members in rice genome. So far, how the OsPSK functions and regulates in vivo is remaining unclear. In this study, we first did structural comparison and phylogenetic analysis of the 7-OsPSK-gene family via bioinformatics. Based on the phylogenetic analysis of the PSK genes in rice and Arabidopsis, we draw the conclusion that the formation of two paralogous PSK genes from the ancestral one was earlier than the monocotyledon-dicotyledon divergence; in addition, OsPSK1 and the rest OsPSK2-OsPSK7 stemmed from two different ancestors. Interrogating expression profiles of each OsPSK family member in different tissues showed different genes with different expression patterns. By means of the method of particle bombardment, we developed an OsPSK3 transgenic line, and further put much effort on studying rice growth under OsPSK3 overexpression background. It showed that the OsPSK3 overexpression line, OsPSK3ox increased OsPSK3 expression about 40% over the wild type, and presented obvious growth vigor with more fibrous roots and more root hairs at seedling stage. Plant height of OsPSK3ox-1 was higher from seedling to the full ripe stage. Notably in chloro-phyll content of leaves, OsPSK3ox plants increased 2.3 times over that of the wild type.
[1] Matsubayashi Y, Sakagami Y. Phytosulfokine, sulfated peptides that induce the proliferation of single mesophyll cells of Asparagus officinalis L.. Proc Natl Acad Sci USA, 1996, 93(15): 7623-7627.
[2] Stuart R, Street HE. Studies on the growth in culture of plant cells: IV. The initiation of division in suspensions of stationary-phase cells of Acer pseudoplatanus L.. J Exp Bot, 1969, 20(3): 556-571.
[3] Yang HP, Matsubayashi Y, Nakamura K, Sakagami Y. Diversity of Arabidopsis genes encoding precursors for phytosulfokine, a peptide growth factor. Plant Physiol, 2001, 127(3): 842-851.
[4] Yang HP, Matsubayashi Y, Nakamura K, Sakagami Y. Oryza sativa PSK gene encodes a precursor of phytosulfokine-α, a sulfated peptide growth factor found in plants. Proc Natl Acad Sci USA, 1999, 96(23): 13560-13565.
[5] Yang G, Shen S, Kobayashi T, Matsubayashi Y, Sakagami Y, Kamada H. Stimulatory effects of a novel peptidyl plant growth factor, phytosulfokine-α, on the adventitious bud formation from callus of Antirrhinum majs L.. Plant Biotechnol, 1999, 16(3): 231-234.
[6] Lorbiecke R, Sauter M. Comparative analysis of PSK peptide growth factor precursor homologs. Plant Sci, 2002, 163(2): 321-332.
[7] Igasaki T, Akashi N, Ujino-Ihara T, Matsubayashi Y, Sakagami Y, Shinohara K. Phytosulfokine stimulates somatic embryogenesis in Cryptomeria japonica. Plant Cell Physiol, 2003, 44(12): 1412-1416.
[8] Hanai H, Matsuno T, Yamamoto M, Matsubayashi Y, Kobayashi T, Kamada H, Sakagami Y. A secreted peptide growth factor, phytosulfokine, acting as a stimulatory factor of carrot somatic embryo formation. Plant Cell Physiol, 2000, 41(1): 27-32.
[9] Matsubayashi Y, Morita A, Matsunaga E, Furuya A, Hanai N, Sakagami Y. Physiological relationships between auxin, cytokinin, and a peptide growth factor, phytosulfokine-α, in stimulation of asparagus cell proliferation. Planta, 1999, 207(4): 559-565.
[10] Matsubayashi Y, Takagi L, Omura N, Morita A, Sakagami Y. The endogenous sulfated pentapeptide phytosulfokine-stimulates tracheary element differentiation of isolated mesophyll cells of zinnia. Plant Physiol, 1999, 120(4): 1043-1048.
[11] Chen YF, Matsubayashi Y, Sakagami Y. Peptide growth factor phytosulfokine-α contributes to the pollen population effect. Planta, 2000, 211(5): 752-755.
[12] Kutschmar A, Rzewuski G, Stührwohldt N, Beemster GTS, Inzé D, Sauter M. PSK-αpromotes root growth in Arabidopsis. New Phytol, 2009, 181(4): 820?831. [13] Yamakawa S, Sakuta C, Matsubayashi Y, Sakagami Y, Kamada H, Satoh S. The promotive effects of a peptidyl plant growth factor, phytosulfokine-α, on the formation of adventitious roots and expression of a gene for a root-specific cystatin in cucumber hypocotyls. J Plant Res, 1998, 111(3): 453?458. [14] Yamakawa S, Matsubayashi Y, Sakagami Y, Kamada H, Satoh S. Promotion by a peptidyl growth factor, phytosulfokine, of chlorophyll formation in etiolated cotyledon of cucumber. Biosci Biotech Bioch, 1998, 62(12): 2441?2443. [15] Matsubayashi Y, Ogawa M, Kihara H, Niwa M, Sakagami Y. Disruption and overexpression of Arabidopsis phytosulfokine receptor gene affects cellular longevity and potential for growth. Plant Physiol, 2006, 142(1): 45?53. [16] Lorbiecke R, Steffens M, Tomm JM, Scholten S, von Wiegen P, Kranz E, Wienand U, Sauter M. Phytosulphokine gene regulation during maize (Zea mays L.) reproduction. J Exp Bot, 2005, 56(417): 1805?1819. [17] Chen L, Zhang S, Beachy RN, Fauquet CM. A protocol for consistent, large-scale production of fertile transgenic rice plants. Plant Cell Rep, 1998, 18(1?2): 25?31. [18] Marone M, Mozzetti S, Ritis DD, Pierelli L, Scambia G. Semiquantitative RT-PCR analysis to assess the expression levels of multiple transcripts from the same sample. Biol Proced Online, 2001, 3(1): 19?25
. [19] Matsubay
