Soybean cyst nematode (SCN) is one of the most devastating pathogen for soybean. Therefore, identification of resistant germplasm resources and resistant genes is needed to improve SCN resistance for soybean. Soybean varieties Huipizhiheidou and Wuzhaiheidou were distributed in China and exhibited broad spectrums of resistance to various SCN races. In this study, these two resistant varieties, combined with standard susceptible varieties (Lee and Essex), were utilized to identify the differentially expressed transcripts after infection with SCN race 4 between resistant and susceptible reactions by using the Affymetrix Soybean Genome GeneChip. Comparative analyses indicated that 21 common genes changed significantly in the resistant group, of which 16 increased and 5 decreased. However, 12 common genes changed significantly in the susceptible group, of which 9 increased and 3 decreased. Additionally, 27 genes were found in common between resistant and susceptible reactions. The 21 significantly changed genes in resistant reaction were associated with disease and defense, cell structure, transcription, metabolism, and signal transduction. The fold induction of 4 from the 21 genes was confirmed by quantitative RT-PCR (qRTPCR) analysis. Moreover, the gene ontology (GO) enrichment analyses demonstrated the serine family amino acid metabolic process and arginine metabolic process may play important roles in SCN resistance. This study provided a new insight on the genetic basis of soybean resistance to SCN race 4, and the identified resistant or resistant-related genes are potentially useful for SCN-resistance breeding in soybean.

Carbohydrate partitioning from source to sink tissues is critical for plant growth and development. However, in maize (Zea mays L.), the molecular mechanisms of callose synthase gene regulating this process have seldom been reported.  Here, we show that the mutation of maize callose synthase12 (ZmCals12) caused increased accumulation of carbohydrate in the photosynthetic leaves but reduced carbohydrate content in sink tissues, which led to plant dwarfing and male sterile.  Histochemical GUS activity assay and mRNA in situ hybridization (ISH) indicated that ZmCals12 was mainly expressed in the vascular transport system.  Loss-of-function of ZmCals12 reduced callose synthase activity and callose deposition in plasmodesmatas (PDs) and around phloem cells (PCs) of vascular bundle.  The drop-and-see (DANS) assay revealed that the PD permeability in the photosynthetic cells and the transport competence of leaf veins were reduced in the Zmcals12 mutants, which led to the reduced symplastic transport.  Paraffin section experiment revealed that less-developed vascular cells (VCs) in the Zmcals12 mutants potentially disturbed sugar transport, thus resulting in the pleiotropic phenotype of the Zmcals12 mutants.  In addition, the impaired sugar transport hindered the internode development by inhibiting auxin (IAA) biosynthesis and signaling in the Zmcals12 mutant.  Collectively, our results provide insights into the mechanism of ZmCals12-mediated callose deposition and symplastic transport governing maize growth and development.