Protective Role of Leaf Variegation in Pittosporum tobira under Low Temperature: Insights into the Physio-Biochemical and Molecular Mechanisms

Leaf variegation has been demonstrated to have adaptive functions such as cold tolerance. Pittosporum tobira is an ornamental plant with natural leaf variegated cultivars grown in temperate regions. Herein, we investigated the role of leaf variegation in low temperature responses by comparing variegated “Variegatum” and non-variegated “Green Pittosporum” cultivars. We found that leaf variegation is associated with impaired chloroplast development in the yellow sector, reduced chlorophyll content, strong accumulation of carotenoids and high levels of ROS. However, the photosynthetic efficiency was not obviously impaired in the variegated leaves. Also, leaf variegation plays low temperature protective function since “Variegatum” displayed strong and efficient ROS-scavenging enzymatic systems to buffer cold (10 °C)-induced damages. Transcriptome analysis under cold conditions revealed 309 differentially expressed genes between both cultivars. Distinctly, the strong cold response observed in “Variegatum” was essentially attributed to the up-regulation of HSP70/90 genes involved in cellular homeostasis; up-regulation of POD genes responsible for cell detoxification and up-regulation of FAD2 genes and subsequent down-regulation of GDSL genes leading to high accumulation of polyunsaturated fatty acids for cell membrane fluidity. Overall, our results indicated that leaf variegation is associated with changes in physiological, biochemical and molecular components playing low temperature protective function in P. tobira.

Cambios ultraestructurales en blastosporas de Taphrina caerulescens en presencia de hospedante susceptible y no susceptible

<em>Taphrina caerulescens</em> es un hongo fitopatógeno de encinos, que causa ampollas en hojas de 50 especies de <em>Quercus</em>. En 2015, el hongo se aisló por primera vez de <em>Quercus eduardii</em>, especie de encino endémica de la Sierra Fría de Aguascalientes, México. El objetivo de este estudio fue documentar los cambios que se producen en el inóculo fúngico antes de la infección de su hospedante a medida que cambia de saprófito a parásito. Se utilizaron dos especies de plantas hospedantes: <em>Q. eduardii</em> y <em>Q. potosina</em>, y una especie no hospedante, <em>Pittosporum tobira</em>. En el microscopio electrónico de barrido se analizaron muestras de hojas 24 h, 48 h y 72 h post inoculación con una suspensión de conidios de <em>T. caerulescens</em>. Se observó una gemación moderada de conidios después de 24 h en muestras de <em>Quercus</em>; después de 48 h la gemación incrementó en las dos especies de <em>Quercus</em> y se observó la formación de blastosporas significativamente más pequeñas, que el inóculo original en las muestras de <em>Quercus eduardii</em>. La formación de tubos germinativos de las blastosporas pequeñas se comprobó después de 48 h en <em>Quercus</em> <em>eduardii</em>. Los tubos germinativos se observaron creciendo de manera aleatoria hacia las estomas. No se observaron cambios significativos en las muestras no hospedantes. No existe otro reporte de blastosporas pequeñas en <em>T. caerulescens</em>.

İstanbul İli Adalar İlçesi’nde Hobi Bahçeleri ve Peyzaj Alanlarında Yetiştirilen Süs Bitkilerinde Tospovirüslerin Saptanması

This study was conducted in order to detect Tomato spotted wilt virus (TSWV), Irish yellow spot virus (IYSV) and Impatients necrotic spot virus (INSV) in ornamental plants growing in hobby gardens and landscaping areas in Adalar district (Büyükada, Heybeliada, Kınalıada and Burgazada) of Istanbul province between 2015 and 2016. During the surveys carried out in that district, the samples were collected from both simptomatologically suspicious ornamental plants and the plants which did not show any symptoms. All of the collected samples (n=150) were firstly tested by Double Antibody Sandwich (DAS) ELISA and none of the samples were found to be infected with TSWV and INSV. The samples detected to be positive with IYSV by ELISA tests were then used in RT-PCR studies. At the RT-PCR using the IYSV-465c; IYSV-239f primer pair, a band with a size of 240 bp was observed for Pittosporum tobira and Hydrangea macrophylla. Therefore, the presence of IYSV infection in Adalar was also confirmed molecularly.