Plant Biology Commons^™

Summer Heat And An Epidemic Of Cytospora Canker Of Alnus, James J. Worrall, Gerard C. Adams, Sarah C. Tharp

Department of Plant Pathology: Faculty Publications

An epidemic of cytospora canker [Valsa melanodiscus, anamorph Cytospora umbrina] is associated with dieback and mortality of Alnus incana ssp. tenuifolia in the Southern Rocky Mountains and had begun by the late 1980s. Isolations showed that inoculum was often abundant on bark and bud surfaces even in winter, especially near diseased stems. The pathogen was occasionally isolated from internal tissues of dormant buds and asymptomatic wood and phloem. In infected stems, the pathogen was detected up to 5 cm beyond visible canker margins. The data suggest that the pathogen can cause latent infections, but the infection court …

Post-­Fire Alterations In Mechanical Strength Of Leaves In Heteromeles Arbutifolia, Andrew Hair, Madeline Dilascia, Nick Novella, Taylor Wurdeman

Featured Research

Wildfires in the Santa Monica mountains in Southern California burn down a decent percentage of the local vegetation. However, some plants like Heteromeles Arbutifolia, are considered to be resprouters because they return a mere two years after being burnt down. It is hypothesized that the artificially browsed resprout leaves will have a lower tensile strength than both the young and adult leaves because they use a lower amount of carbohydrates per unit-leaf-area. Data showed that although there was a slight different between the young leaves and the adult leaves of the Heteromeles, there was no statistically significant difference between the …

A Comparison Of The Tensile Strength Of Leaves In Encelia Californica In Canyon And Beach Species, Anna Chowaniec, Annie Lee, Hayley Springs

Featured Research

Our research is concerned with the further exploration of leaf biomechanics, a relatively unexamined field. The purpose of this experiment was to find a correlation between environmental stress factors and tensile strength of leaves of Encelia californica. We hypothesized the beach species would have a higher tensile strength than canyon species. After evaluating data collected from both Pepperdine’s Presidents Canyon and Malibu beach we found that while the canyon species could withstand a higher maximum load of force, there was no difference between the canyon and the beach species with leaf area taken into account. Using Young’s Modulus, we …

Turnover Of Mature Mirnas And Sirnas In Plants And Algae, Heriberto Cerutti, Fadia Ibrahim

Center for Plant Science Innovation: Faculty Publications

rnicroRNAs (miRNAs) and small interfering RNAs (siRNAs) play important roles in gene regulation and defense responses against transposons and viruses in eukaryotes. These small RNAs generally trigger the silencing of cognate sequences through a variety of mechanisms, including RNA degradation, translational inhibition, and transcriptional repression. In the past few years, the synthesis and the mode of action of miRNAs and siRNAs have attracted great attention. However, relatively little is known about mechanisms of quality control during small RNA biogenesis as well as those that regulate mature small RNA stability. Recent studies in Arabidopsis thaliana and Caenorhahditis elegans have implicated 3′-to-5′ …

Translational Inhibition By Micrornas In Plants, Bin Yu, Hai Wang

Center for Plant Science Innovation: Faculty Publications

MicroRNAs (miRNAs) are 21–24 nucleotide riboregulators, which selectively repress gene expression through transcript cleavage and/or translational inhibition. It was thought that most plant miRNAs act through target transcript cleavage due to the high degree of complementarity between miRNAs and their targets. However, recent studies have suggested widespread translational inhibition by miRNAs in plants. The mechanisms underlining translational inhibition by plant miRNAs are largely unknown, but existing evidence has indicated that plants and animals share some mechanistic similarity of translational inhibition. Translational inhibition by miRNAs has been shown to regulate floral patterning, floral timing, and stress responses. This chapter covers recent …

Effect Of Fertilizer On Leaf Tensile Strength In Salvia Leucophylla, Tawny Lindahl, John Buie, Eiichiro Uemura

Featured Research

This experiment sought to establish a connection between short term growth in Salvia leucophylla found in Southern California and nutrient availability in the soil. It was hypothesized that adding artificially produced nutrient mix Miracle Grow would increase the strength of the leaves in the herb after one week of addition. Newer leaves were tested in the Instron device for tensile strength after one week, and after data analysis, it was concluded that there was no difference in tensile strength of leaves treated with fertilizer compared with leaves without fertilizer.

Differences In Hydraulic Conductance (Kh) As A Function Of Leaf Area (Ks Leaf) And Xylem Size (Ks Xylem) In Encelia Californica And Venegasia Carpesioides, Tony Audin, Andrew Dudley, Janel Gonzalez

Featured Research

Southern California and the Santa Monica Mountains experience a climate similar to that of the Mediterranean basin. This means hot, dry summers, mild, wet winters, and large amounts of plant diversity. A major issue that can affect these regions is water availability and processing. To demonstrate this, hydraulic conductance (Kh) was measured as a function of leaf area (KS Leaf) and xylem size (KS Xylem). Two vascular plants were used for this study, Encelia californica and Venegasia carpesioides. This is because they are similar morphologically but are different genus and species. It was hypothesized that the larger plant (V. carpesioides) …

The Affect Of Temperature On The Fluorescence Of Heteromeles Arbutifolia (Hollywood) In The Santa Monica Mountains, Patrick Y. Chisum, Adam S. Graham, Arthur C. Sanders

Featured Research

Presented here is a comparison of the predawn fluorescence of adult Heteromeles arbutifolia growing on the Pepperdine Seaver campus next to the lacrosse field, and adult Heteromeles growing in Tapia canyon. The analysis of the leaf temperature measured by an IR thermometer showed an average of 9.32°C drop when measuring plants in Tapia canyon compared to those growing on the warmer Pepperdine campus. The air temperature measured by the Kestrel and IR thermometer showed Tapia canyon being an average of 7.27°C colder than predawn measurements on Pepperdine campus. Finally, the fluorescence of the plants in both locations was measured using …

Effect Of Petiole-­To-­Branchlet Angle On Tensile Stress And Tensile Strength In Heteromeles Arbutifolia, Matt W. Andrus, Anthony P. Lisankis, Valen C. Anderson

Featured Research

Heteromeles arbutifolia an important chaparral species of southern California, Is a food source for mule deer (Odocoileus hemionus). This predation has become more pronounced as the climate shifts to hotter, drier, and longer summers. Other species that the deer normally feed on cannot survive these harsh conditions, while Heteromeles arbutifolia is able to persevere (Letourneau, 2004). We decided that there must be mechanisms involved in the petiole of leafs to keep them from being pulled off by deer and strong winds. Our group hypothesized that as the angle between the petiole and branchlet increased, the tensile strength of the petiole …

Comparing Leaf Properties Of Inland And Coastal Malosma Laurina In The Santa Monica Mountains, Rosemary Busch Conn, Lauren Parker, Brittany Sawrey

Featured Research

Our group chose Malosma laurina, commonly known as Laurel Sumac, to observe and test. We hypothesized that there would be difference in photosynthetic trade-offs and capabilities between coastal and inland populations, specifically with respect to leaves. This was based on the low freezing tolerance in Malosma laurina (Pratt et al. 2005), and hypothesized that based on this stress, resources would be allocated differently in inland leaves than in coastal leaves. This hypothesis was tested using the indices of Normalized Difference Vegetation Index (NDVI), the Photochemical Reflectance Index (PRI), the ratio of green to red reflectance, and Leaf Specific Area …

Tensile Strength Of Malosma Laurina Leaves In Wet And Dry Conditions, T. Candelore, N. Despenza, L. Garrison, L. Hinther

Featured Research

Pepperdine University is one located in one of the most diverse places of the world. It is located in the Mediterranean which occupies less than 5% of the earth's landmass and is only found in five areas which includes California. On the campus there are several canyons. One of the canyons is called Winter Canyon. The canyon contained a plant called Malosma laurina which is located in a riparian environment and a chaparral environment. The plant grows in both areas however, our hypothesis was that the dry plants' leaves would demonstrate more plasticity. The soil humidity was also measured to …

Root Tensile Strength In A Native And Non-­Native Species Of The Coastal Chaparral Community, Jamie Elmquist, Andrea Lim, Amanda Scholl, Amanda Vest

Featured Research

Non-­native species are regularly introduced into environments in which they replace existing native species and drastically influence the ecological characteristics of the area and the habitat of the living organisms surrounding them. In the botanical field of study, invasive plant species can choke out native species thus making them endangered or extinct. Specifically in the Santa Monica Mountains of Southern California, there are over 300 non-­native species of plants, each the source of its own repercussions and having both positive and negative effects on the environment. One specific non-­native species, Carpobrotus edulis (ice plant) replaces the native Coreopsis gigante (giant …

An Integrative Approach To Genomic Introgression Mapping, Andrew J. Severin, Gregory A. Peiffer, Wayne W. Xu, D. L. Hyten, Bruna Bucciarelli, Jamie A. O'Rourke, Yung-Tsi Bolon, David Grant, Andrew Farmer, Gregory D. May, Carroll P. Vance, Randy C. Shoemaker, Robert M. Stupar

Department of Agronomy and Horticulture: Faculty Publications

Near-isogenic lines (NILs) are valuable genetic resources for many crop species, including soybean (Glycine max). The development of new molecular platforms promises to accelerate the mapping of genetic introgressions in these materials. Here, we compare some existing and emerging methodologies for genetic introgression mapping: single-feature polymorphism analysis, Illumina GoldenGate single nucleotide polymorphism (SNP) genotyping, and de novo SNP discovery via RNA-Seq analysis of next-generation sequence data. We used these methods to map the introgressed regions in an iron-inefficient soybean NIL and found that the three mapping approaches are complementary when utilized in combination. The comparative RNA-Seq approach offers …

Soydb: A Knowledge Database Of Soybean Transcription Factors, Zheng Wang, Marc Libault, Trupti Joshi, Babu Valliyodan, Henry T. Nguyen, Dong Xu, Gary Stacey, Jianlin Cheng

Department of Agronomy and Horticulture: Faculty Publications

Background: Transcription factors play the crucial rule of regulating gene expression and influence almost all biological processes. Systematically identifying and annotating transcription factors can greatly aid further understanding their functions and mechanisms. In this article, we present SoyDB, a user friendly database containing comprehensive knowledge of soybean transcription factors.

Description: The soybean genome was recently sequenced by the Department of Energy-Joint Genome Institute (DOE-JGI) and is publicly available. Mining of this sequence identified 5,671 soybean genes as putative transcription factors. These genes were comprehensively annotated as an aid to the soybean research community. We developed SoyDB - a knowledge database …

Transgenic Maize Lines With Cell-Type Specific Expression Of Fluorescent Proteins In Plastids, Amir Sattarzadeh, Jonathan Fuller, Salvador Moguel, Katia Wostrikoff, Shirley Sato, Sarah Covshoff, Tom Clemente, Maureen Hanson, David Stern

Department of Agronomy and Horticulture: Faculty Publications

Plastid number and morphology vary dramatically between cell types and at different developmental stages. Furthermore, in C4 plants such as maize, chloroplast ultrastructure and biochemical functions are specialized in mesophyll and bundle sheath cells, which differentiate acropetally from the proplastid form in the leaf base. To develop visible markers for maize plastids, we have created a series of stable transgenics expressing fluorescent proteins fused to either the maize ubiquitin promoter, the mesophyll-specific phosphoenolpyruvate carboxylase (PepC) promoter, or the bundle sheath-specific Rubisco small subunit 1 (RbcS) promoter. Multiple independent events were examined and revealed that maize codon-optimized versions of YFP and …

Comparative Leaf Decomposition Rates Including A Non-Native Species In An Urban Ozark Stream, Sarah E. Lewis, Arthur V. Brown

Journal of the Arkansas Academy of Science

Leaf decomposition of three species of native Ozark vegetation was compared to that of one nonnative invasive species. Leaves were placed in an urban gravel-bed stream for 23 days. Changes in mass and condition of the leaves were assessed along with stream temperature, flow, width, depth and discharge. Species native to Eastern North American forests were sycamore (Platanus occidentalis), dogwood (Cornus florida), and redbud (Cercis canadensis). The nonnative species, Japanese (Amur) honeysuckle (Lonicera maackii) comprised approximately 80% of the understory vegetation within the riparian zone of the study reach. After 23 days, Sycamore lost 24.6% mass, dogwood lost 30%, redbud …

The Pathogenicity Determinant Of Citrus Tristeza Virus Causing The Seedling Yellows Syndrome Maps At The 3′-Terminal Region Of The Viral Genome, Maria R. Albiach-Marti, Cecile J. Robertson, Siddarame Gowda, Satyanarayana Tatineni, Belen Belliure, Stephen M. Garnsey, Svetlana Y. Folimonova, Pedro Moreno, William O. Dawson

Department of Plant Pathology: Faculty Publications

Citrus tristeza virus (CTV) (genus Closterovirus, family Closteroviridae) causes some of the more important viral diseases of citrus worldwide. The ability to map disease-inducing determinants of CTV is needed to develop better diagnostic and disease control procedures. A distinctive phenotype of some isolates of CTV is the ability to induce seedling yellows (SY) in sour orange, lemon and grapefruit seedlings. In Florida, the decline isolate of CTV, T36, induces SY, whereas a widely distributed mild isolate, T30, does not. To delimit the viral sequences associated with the SY syndrome, we created a number of T36/T30 hybrids by substituting T30 …

Heterologous Minor Coat Proteins Of Citrus Tristeza Virus Strains Affect Encapsidation, But The Coexpression Of Hsp70h And P61 Restores Encapsidation To Wild-Type Levels, Satyanarayana Tatineni, Siddarame Gowda, William O. Dawson

Department of Plant Pathology: Faculty Publications

The long flexuous bipolar virions of Citrus tristeza virus (CTV), a Closterovirus, are encapsidated with two capsid proteins at opposite ends: the minor coat protein (CPm) encapsidates the 5′ 630 nts of the genomic RNA and the major coat protein encapsidates the remainder of the genome. In this study, we found encapsidation of CTV CPm in the absence of other assembly-related proteins is highly specific in contrast to most plant viruses that allow virion assembly by a range of heterologous coat proteins. Heterologous CPms with 95–96% amino acid identity from related strains in CTV-CPm, a replicon with CPm as …

Soil And Root Populations Of Fluorescent Pseudomonas Spp. Associated With Seedlings And Field-Grown Plants Are Affected By Sorghum Genotype, Deanna L. Funnell-Harris, Jeffrey F. Pedersen, Scott E. Sattler

Department of Plant Pathology: Faculty Publications

Sorghum [Sorghum bicolor (L.) Moench] is valued for bioenergy, feed and food. Potential of sorghum genotypes to support differing populations of root- and soil-associated fluorescent Pseudomonas spp. or Fusarium spp., in two soils, was assessed. Culturable pseudomonads were enumerated from roots and soil of sorghum (Redlan and RTx433) and wheat (Lewjain) seedlings repeatedly grown in cycled soils in the growth chamber. Pseudomonads and Fusarium spp. were assessed from roots and soil of field-grown sorghum along with biological control traits hydrogen cyanide (HCN) and 2,4-diacetylphlorogluconol (phl) production. After four 4-week cycles, soil associated with Redlan seedlings had greater numbers …

Brown Midrib Mutations And Their Importance To The Utilization Of Maize, Sorghum, And Pearl Millet Lignocellulosic Tissues, Scott E. Sattler, Deanna L. Funnell-Harris, Jeffrey F. Pedersen

Department of Plant Pathology: Faculty Publications

Brown midrib mutants have been isolated in maize (Zea mays), sorghum (Sorghum bicolor) and pearl millet (Pennisetum glaucum) arising by either spontaneous or chemical mutagenesis. The characteristic brown coloration of the leaf mid veins is associated with reduced lignin content and altered lignin composition, traits useful to improve forage digestibility for livestock. Brown midrib phenotype is correlated with two homologous loci in maize (bm1 and bm3) and sorghum (bmr6 and bmr12), which encode cinnamyl alcohol dehydrogenase (CAD) and a caffeic O-methyl transferase (COMT). These enzymes are involved in the last …