3.5 Impact of drought stress on tapetum-specific expressed genes
To determine whether drought affected the development of the tapetum and microspore at transcription level, 52 tapetum- and pollen- related expressed genes were identified (Table S8). RNA-Seq data showed thatSolanum lycopersicum EXCESS MICROSPORES (SlEMS ),ABORTED MICROSPORES (SlAMS ), DEFECTIVE TAPETUM DEVELOPMENT and FUNCTION1 (SlDTF1) DYSFUNCTIONAL TAPETUM1 (SlDYT1) and CALLOSE DEFECTIVE MICROSPORE1 (SlCDM1 ) were markedly down-regulated whereas SlMYB80 was up-regulated under DS condition at PMC-MEI stage. At TED-VUM stage, SlAMS , MALE STERILITY1 (SlMS1 ) and ANTHER 7 (SlAT7) were significantly drought-repressed (Figure 5). The up-regulation of at most a gene at PMC-MEI stage while all examined genes were down-regulated at TED-VUM stage is in line with the considerable amount of damage to the tapetum and/or microspores caused by drought stress in anthers at TED-VUM stage than at PMC-MEI stage as revealed by histo-cytological analysis and suggest a dominant and positive role of SlMYB80 in drought tolerance mechanism early in anther development.