Preliminary Characterization of Function of Rac /Rop GEF1 in Arabidopsis

[Objective]The aim was to research the function of AtGEF1 in Rac/Rop GTPses mediate auxin signal passway.[Method]Using the transgenic plants of AtGEF1 promotor fused with GUS reporter gene and the over-expression plants of Rac/Rop GEF1 under the control of 35S promoter as materials,which were constructed from our lab,the expression pattern of GEF1 was analyzed by GUS assay using histochemical staining,and the development of seedling roots of over-expression plant of GEF1 was observed.[Result]GEF1 expression was mainly detected in root meristem,root vascular tissue,lateral roots and root hair.Furthermore,the expression level of GEF1 was highly increased with the induction of NAA.Over-expression of GEF1 was observed to enhance lateral root formation.[Conclusion]GEF1 may be involved in the regulation of development of root and root hair,and it may have redundant function in the control of lateral root development.

MPK14-mediated auxin signaling controls lateral root development via ERF13-regulated very-long-chain fatty acid biosynthesis

Auxin plays a critical role in lateral root(LR)formation.The signaling module composed of auxin-response factors(ARFs)and lateral organ boundaries domain transcription factors mediates auxin signaling to control almost every stage of LR development.Here,we show that auxin-induced degradation of the APETALA2/Ethylene Responsive Factor(AP2/ERF)transcription factor ERF13,dependent on MITOGENACTIVATED PROTEIN KINASE MPK14-mediated phosphorylation,plays an essential role in LR development.Overexpression of ERF13 results in restricted passage of the LR primordia through the endodermal layer,greatly reducing LR emergence,whereas the erf13 mutants showed an increase in emerged LR.ERF13 inhibits the expression of 3-ketoacyl-CoA synthase16(KCS16),which encodes a fatty acid elongase involved in very-long-chain fatty acid(VLCFA)biosynthesis.Overexpression of KCS16 or exogenous VLCFA treatment rescues the LR emergence defects in ERF13 overexpression lines,indicating a role downstream of the auxin-MPK14-ERF13 signaling module.Collectively,our study uncovers a novel molecular mechanism by which MPK14-mediated auxin signaling modulates LR development via ERF13-regulated VLCFA biosynthesis.

Molecular Basis of Unique Branching Phenotypes in Salvia splendens and the Role of PSY

The branching system of higher plants plays a very important role in plant morphogenesis,and the number of branches can directly affect crop yield and the ornamental value of plants.It is a complicated development process involving complex molecular mechanisms.The‘Cailinghong’variety of Salvia splendens is characterized by its great branching ability with the ability to grow into a spherical form naturally,without pinching.To gain insight into the molecular events during the branching development of S.splendens,suppressive subtractive hybridization(SSH)technology was used to screen differentially expressed genes between the erect plant type(strain 35)and the spherical plant type(‘Cailinghong’).In total,96 and 116 unigenes were annotated.Four and eight unigenes up-regulated in‘Cailinghong’and strain 35,respectively,were associated with plant hormone anabolism and signal transduction,suggesting that they participate in the branching process.One of these genes,phytoene synthase(PSY),is a precursor of the new plant hormone group strigolactones.Using the PSY fragment(192 bp)as a template,the cDNA sequence of PSY in S.splendens was cloned and named SsPSY.A relative expression analysis and transgenic test results indicated that SsPSY plays an important role in lateral branch development in‘Cailinghong’.These results provide new insight into the molecular mechanisms underlying branching in S.splendens.

Historical Evolution of Traditional Medicine in Japan

Traditional Japanese Medicine originated from traditional Chinese medicine and was first introduced to Japan directly from the mainland of China or the Korean Peninsula.After its dissemination,integration,adaption,and development in Japan for generations,it had evolved into Kampo medicine with Japanese characteristics and taken a leading role in Japanese medical practice.In history,there appeared successively schools such as Followers of Later Developments in Medicine,Followers of Classic Methods,Integrated School,and School of Textual Research.Alter Meiji Restoration,Kampo medicine experienced a tremendous impact by western medicine.However after World War II,with unremitting endeavors from learned scholars,traditional Japanese medicinje was revived again.

Brassinosteroids Regulate Root Growth, Development, and Symbiosis

Brassinosteroids （BRs） are natural plant hormones critical for growth and development. BR-deficient or signaling mutants show significantly shortened root phenotypes. But for a long time, it was thought that these phenotypes were solely caused by reduced root cell elongation in the mutants. Functions of BRs in regulating root development have been largely neglected. Recent detailed analyses, however, revealed that BRs are not only involved in root cell elongation but are also involved in many aspects of root development, such as maintenance of meristem size, root hair formation, lateral root initiation, gravitropic response, mycorrhiza formation, and nodulation in legume species. In this review, current findings on the functions of BRs in mediating root growth, development, and symbiosis are discussed.

Notes from the Underground:Receptor-Like Kinases in Arabidopsis Root Development

During plant development, the frequency and context of cell division must be controlled, and cells must differentiate properly to perform their mature functions. In addition, stem cell niches need to be maintained as a reservoir for new cells. All of these processes require intercellular signaling, whether it is a cell relaying its position to other cells, or more mature cells signaling to the stem cell niche to regulate the rate of growth. Receptor-like kinases have emerged as a major component in these diverse roles, especially within the Arabidopsis root. In this review, the functions of receptor-like kinase signaling in regulating Arabidopsis root development will be examined in theareas of root apical meristem maintenance, regulation of epidermal cell fate, lateral root development and vascular differentiation.

Phloem-Mobile AuxlIAA Transcripts Target to the Root Tip and Modify Root Architecture

In plants, the phloem is the component of the vascular system that delivers nutrients and transmits signals from mature leaves to developing sink tissues. Recent studies have identified proteins, mRNA, and small RNA within the phloem sap of several plant species. It is now of considerable interest to elucidate the biological functions of these potential long-distance signal agents, to further our understanding of how plants coordinate their developmental programs at the whole-plant level. In this study, we developed a strategy for the functional analysis of phloem-mobile mRNA by focusing on IAA transcripts, whose mobility has previously been reported in melon （Cucumis melo cv. Hale＇s Best Jumbo）. Indoleacetic acid （IAA） proteins are key transcriptional regulators of auxin signaling, and are involved in a broad range of developmental processes including root development. We used a combination of vasculature-enriched sampling and hetero-grafting techniques to identify IAA18 and IAA28 as phloemmobile transcripts in the model plant Arabidopsis thaliana. Micro-grafting experiments were used to confirm that these IAA transcripts, which are generated in vascular tissues of mature leaves, are then transported into the root system where they negatively regulate lateral root formation. Based on these findings, we present a model in which auxin distribution, in combination with phloem-mobile Aux/IAA transcripts, can determine the sites of auxin action.