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On infection, plant‐parasitic nematodes establish feeding sites in roots from which they take up carbohydrates among other nutrients. Knowledge on how carbohydrates are supplied to the nematodes' feeding sites is limited. Here, gene expression analyses showed that RNA levels of OsSWEET11 to OsSWEET15 were extremely low in both Meloidogyne graminicola (Mg)‐caused galls and noninoculated roots. All the rice sucrose transporter genes, OsSUT1 to OsSUT5, were either down‐regulated in Mg‐caused galls compared with noninoculated rice roots or had very low transcript abundance. OsSUT1 was the only gene up‐regulated in galls, at 14 days postinoculation (dpi), after being highly down‐regulated at 3 and 7 dpi. OsSUT4 was down‐regulated at 3 dpi. No noticeable OsSUTs promoter activities were detected in Mg‐caused galls of pOsSUT1 to ‐5::GUS rice lines. Loading experiments with carboxyfluorescein diacetate (CFDA) demonstrated that symplastic connections exist between phloem and Mg‐caused giant cells (GCs). According to data from OsGNS5‐ and OsGSL2‐overexpressing rice plants that had decreased and increased callose deposition, respectively, callose negatively affected Mg parasitism and sucrose supply to Mg‐caused GCs. Our results suggest that plasmodesmata‐mediated sucrose transport plays a pivotal role in sucrose supply from rice root phloem to Mg‐caused GCs, and OsSWEET11 to ‐15 and OsSUTs are not major players in it, although further functional analysis is needed for OsSUT1 and OsSUT4. [ABSTRACT FROM AUTHOR]

Trichoderma is a soil-borne fungal genus that includes species with a significant impact on agriculture and industrial processes. Some Trichoderma strains exert beneficial effects in plants through root colonization, although little is known about how this interaction takes place. To better understand this process, the root colonization of wild-type Arabidopsis and the salicylic acid ( SA)-impaired mutant sid2 by a green fluorescent protein ( GFP)-marked Trichoderma harzianum strain was followed under confocal microscopy. Trichoderma harzianum GFP22 was able to penetrate the vascular tissue of the sid2 mutant because of the absence of callose deposition in the cell wall of root cells. In addition, a higher colonization of sid2 roots by GFP22 compared with that in Arabidopsis wild-type roots was detected by real-time polymerase chain reaction. These results, together with differences in the expression levels of plant defence genes in the roots of both interactions, support a key role for SA in Trichoderma early root colonization stages. We observed that, without the support of SA, plants were unable to prevent the arrival of the fungus in the vascular system and its spread into aerial parts, leading to later collapse. [ABSTRACT FROM AUTHOR]