[show abstract][hide abstract] ABSTRACT: Expansins are cell wall proteins that promote cell wall loosening by inducing pH-dependent cell wall extension and stress relaxation. Expansins are required in a series of physiological developmental processes in higher plants such as seed germination. Here we identified an Arabidopsis expansin gene AtEXPA2 that is exclusively expressed in germinating seeds and the mutant shows delayed germination, suggesting that AtEXP2 is involved in controlling seed germination. Exogenous GA application increased the expression level of AtEXP2 during seed germination, while ABA application had no effect on AtEXP2 expression. Furthermore, the analysis of DELLA mutants show that RGL1, RGL2, RGA, GAI are all involved in repressing AtEXP2 expression, and RGL1 plays the most dominant role in controlling AtEXP2 expression. In stress response, exp2 mutant shows higher sensitivity than wild type in seed germination, while overexpression lines of AtEXP2 are less sensitive to salt stress and osmotic stress, exhibiting enhanced tolerance to stress treatment. Collectively, our results suggest that AtEXP2 is involved in the GA-mediated seed germination and confers salt stress and osmotic stress tolerance in Arabidopsis.
PLoS ONE 01/2014; 9(1):e85208. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Arabidopsis trichome is a model system for studying cell development, cell differentiation and the cell cycle in plants. Our previous studies have shown that the ZINC FINGER PROTEIN5 (ZFP5) controls shoot maturation and epidermal cell fate through GA signaling in Arabidopsis. We have identified a novel C2H2 zinc finger protein ZINC FINGER PROTEIN 6 (ZFP6) which plays a key role in regulating trichome development in Arabidopsis. Overexpression of ZFP6 results in ectopic trichomes on carpels and other inflorescence organs. Gain- and loss-of-function analyses have shown that the zfp6 mutant exhibits a reduced number of trichomes in sepals of flowers, cauline leaves, lateral branch and main inflorescence stems in comparison to wild-type plants. Molecular and genetic analyses suggest that ZFP6 functions upstream of GIS, GIS2, ZFP8, ZFP5 and key trichome initiation regulators GL1 and GL3.We reveal that ZFP6 and ZFP5 mediate the regulation of trichome initiation by integrating GA and cytokinin signaling in Arabidopsis. These findings provide new insights into the molecular mechanism of plant hormone control of epidermal trichome patterning through C2H2 transcriptional factors.
[show abstract][hide abstract] ABSTRACT: Although root hair development in Arabidopsis thaliana has been extensively studied, it remains unknown whether the zinc finger proteins, the largest family of transcription factors in plants, are involved in this process. Here we report that the C2H2 zinc finger protein ZINC FINGER PROTEIN 5 (ZFP5) is a key regulator of root hair initiation and morphogenesis in Arabidopsis. ZFP5 is mainly expressed in root and preferentially in root hair cells. Using both zfp5 mutants and ZFP5 RNAi lines, we show that reduction in ZFP5 function leads to fewer and much shorter root hairs compared to wild-type. Genetic and molecular experiments demonstrate that ZFP5 exerts its effect on root hair development by directly promoting expression of the CAPRICE (CPC) gene. Furthermore, we show that ZFP5 expression is induced by cytokinin, and that ZFP5 mediates cytokinin and ethylene effects on the formation and growth of root hairs. These results suggest that ZFP5 integrates various plant hormone cues to control root epidermal cell development in Arabidopsis.
[show abstract][hide abstract] ABSTRACT: To gain a better understanding of the protective function of the trichome in Arabidopsis against UV-B radiation, we performed a study using several Arabidopsis trichome mutants (gl1, gis, gis2, zfp8, try82, and gl3), overexpressing trichome positive regulator lines (35S:GIS and 35S:GIS2), and wild-types (WT) under simulated enhanced UV-B radiation conditions. The flowering time, height, diameter of rosette, leaf size, trichome density, and expression levels of GL3 gene were measured. Significant decreases in height, diameter of rosette, leaf size, and a notable delay in flowering time were observed in all mutants and wild-types after exposure to UV-B. Moreover, the trichome density showed a significant increase, suggesting a clear induction of trichome formation by UV-B. Comparing the mutants and WT, we found that the mutants that had more trichomes showed a lower sensitivity to UV-B than the WT, whereas the mutants that had fewer trichomes were more sensitive to UV-B. These results indicated that the trichome plays a key shielding role against UV-B radiation. qRT-PCR analysis indicated that UV-B radiation induced expression of GL3 and an increase in GL3 transcript level correlated with the increase in trichome density and, suggesting a possible role of GL3 by integrating the environmental signal to control trichome initiation.
Journal of photochemistry and photobiology. B, Biology 04/2012; 113:29-35. · 1.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cell differentiation generally corresponds to the cell cycle, typically forming a non-dividing cell with a unique differentiated morphology, and Arabidopsis trichome is an excellent model system to study all aspects of cell differentiation. Although gibberellic acid is reported to be involved in trichome branching in Arabidopsis, the mechanism for such signaling is unclear. Here, we demonstrated that GLABROUS INFLORESCENCE STEMS (GIS) is required for the control of trichome branching through gibberellic acid signaling. The phenotypes of a loss-of-function gis mutant and an overexpressor showed that GIS acted as a repressor to control trichome branching. Our results also show that GIS is not required for cell endoreduplication, and our molecular and genetic study results have shown that GIS functions downstream of the key regulator of trichome branching, STICHEL (STI), to control trichome branching through the endoreduplication-independent pathway. Furthermore, our results also suggest that GIS controls trichome branching in Arabidopsis through two different pathways and acts either upstream or downstream of the negative regulator of gibbellic acid signaling SPINDLY (SPY).
Plant and Cell Physiology 12/2011; 53(2):457-69. · 4.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: Trichomes are specialized structures that develop from epidermal cells in the aerial parts of plants, and are an excellent model system to study all aspects of cell differentiation including cell fate determination, cell cycle regulation, cell polarity and cell expansion. The development of the trichome is a process of integration of both external signals and endogenous developmental programs. During recent years, molecular analysis of trichome development at different stages has been well studied, and through the mutant phenotypes and the function of corresponding genes, the underlying mechanism has been revealed in a first glimpse. This paper offers a mini-view on this integration process with emphasis on the effects of plant hormone signaling on trichome development in plants through GLABROUS INFLORESCENCE STEMS (GIS) family and subfamily genes.