Morphological, biochemical and molecular characterization of sorghum (Sorghum bicolor) genotypes contrasting for phosphate use efficiency.

We compared three Pi-efficient (ATF-14B, ATF-53B, 101B) and four Pi-inefficient (ATF-16B, 116R, 136B, 187R) sorghum genotypes under different Pi concentrations. There were no significant differences between the groups in Pi-use efficiency under Pi-deprivation for anthocyanin accumulation, dry-weight matter, acid phosphatase activity (APA), and aerenchyma formation. However, both groups showed anthocyanin accumulation under Pi-deprivation. Under Pi-deficiency, there was a significant reduction of dry weight in both groups, with no significant differences between contrasting genotypes. All genotypes exhibited a significant increase in root/shoot ratios during Pi-deficiency, and these changes were not related to Pi-use efficiency. The total Pi content in roots and shoots in all genotypes was similar and represented less than 0.2 % of the total dry weight. For all genotypes, the Pi content in P+ treatment resulted in a significant variation ranging from 0.45 to 0.85% and 0.41 to 0.66% in roots and shoots, respectively. The genotype 187R had the highest P content in roots and shoots. APA activity showed increased activity only in the roots of both groups. The development of aerenchyma was conspicuous in the basal and in the middle root sections of all genotypes grown under different Pi levels. Two sorghum Pi-transporter genes were strongly overexpressed in the middle part of Pi-deprived roots of 136B genotype. We did not find differences that explain the Pi-use efficiency between efficient and inefficient genotypes. More studies are needed to elucidate the complex mechanism of P-utilization by sorghum plants

Isolamento e caracterização de genes transportadores de fósforo de alta afinidade em sorgo.

O fosfato (Pi) é um dos macronutrientes essenciais para o crescimento e desenvolvimento das plantas. No entanto, sua disponibilidade é altamente restrita em solos ácidos do Cerrado brasileiro, que são frequentemente usados para o cultivo de sorgo (Sorghum bicolor). Embora vários genótipos contrastantes eficientes e ineficientes do uso de Pi tenham sido obtidos de variantes genéticas naturais, os mecanismos moleculares subjacentes permanecem obscuros. Os transportadores Pi de alta afinidade desempenham um papel fundamental na aquisição de Pi pelas raízes e sua posterior mobilização para partes aéreas. Neste estudo, preparamos uma biblioteca de cDNA a partir de plântulas de sorgo crescidas sob deficiência de Pi que foi escrutinada utilizando-se os transportadores heterólogos de Pi, ZmPTs do milho. Isso possibilitou o isolamento de dois homólogos referidos como SbPT1 (MH333040) e SbPT2 (MH333041) (Sorghum bicolor Phosphate Transporter). A análise de Southern blot revelou que os genes SbPT estão representados por uma pequena família gênica compreendendo cinco a seis membros no genoma do sorgo. Os resultados evidenciaram um aumento significativo nos níveis de transcrição de SbPT1 e SbPT2 nas raízes de genótipos deficientes em Pi. Esses resultados sugerem a regulação transcricional de SbPTs por Pi.bitstream/item/202091/1/bol-189.pd