Liberibacter africanus and Ca. Liberibacter ameri canus. The genome of the Las species was recently published, with a size of approximately 1. 23 Mb. It has been generally accepted that, after infection or inoculation, the HLB bacteria migrate through phloem and, by accu mulating there, causes the formation of sieve plug. Consequently, the transport of nutrients from the source leaves to various sinks are compro mised or even blocked in severely infected plants, leading to the alterations in carbohydrate metabolism for meta bolic flow and exhibiting such phenotypes as yellow and blotchy mottles on leaves, variegated fruits and poor root growth. Because of the huge impact of HLB in the citrus industry, plant pathologists and horticulturists have long sought after the HLB resistance mechanism in citrus.
A recent survey suggests the existence of genetic varia tions Inhibitors,Modulators,Libraries among different citrus species, varieties and stocks. In general, mandarin, sweet orange and grapefruit are relatively more susceptible to the HLB bacterial infection, while sour orange, lemon, lime, and citrange are less suscep tible. This raises the possibility that HLB resistance can be achieved through genetic means. Nevertheless, breeding for the HLB resistance through crossing Inhibitors,Modulators,Libraries will be a daunting task, given the complex genetic backgrounds, the nature of asexual propagation and the relatively long juvenile period for citrus. Therefore, many researchers have turned their attentions to finding the target genes that are required or critical for the citrus host response to the HLB bacteria.
Transcriptome Anacetrapib analysis has been used as a straight forward approach to identify the genes whose ex pression is altered in citrus leaves in response to the HLB inoculation. These studies led to the iden tification of Inhibitors,Modulators,Libraries several hundred or thousand genes that are up or down regulated by the HLB bacterial Inhibitors,Modulators,Libraries infection. The majority of these genes can be grouped into metabolism, transport and response to stimulus. However, these studies varied significantly in terms of study design and data analysis. Furthermore, there is a lack of comparison of the results from these different experiments. In addition, how these HLB bacterium regulated genes are connected in a system remains unknown. To provide a systems view of citrus response to the HLB bacterial infection, we first performed a comparative study of the previously reported transcriptome datasets.
Our results show that there are 21 probe sets are commonly up regulated and a number of genes that are specific to early, late or very late stages of in oculation. Furthermore, using the Pearson correlation coef ficient based unweighted gene coexpression analysis, we constructed an HLB response network. This citrus gene coexpression network consists of 3,507 Probesets and 56,857 interactions.